Arduino Based Soaring Related Devices

[[email protected]]

Over the last two years I've designed and built three Arduino based soaring related devices.. They are: 1) Tow Altitude Recorder with tow plane and ground units, 2) Cockpit Dual Battery Voltage & Temp Monitor, and 3)Trailer Lights Monitor.

The Tow Altitude Recorder tow plane unit records the takeoff time and the tow plane release altitude. The release altitude is recorded automatically based on the highest altitude reached for the tow or manually using the Record Altitude button. The recorded launch time and tow altitude is transmitted to the ground unit once the tow plane is at or below 1000 ft AGL. The ground unit displays the launch time and altitude of the two previous tows but also allows the user to scroll through all tows for the day. Links to photos of the tow plane and ground units are included in this post. Both the tow plane and ground units use backlit sunlight readable LCD displays.

The Cockpit Dual Battery Voltage & Temp Monitor measures and displays the avionics battery voltage and temperature inside the cockpit using a sunlight readable LCD display.

The Trailer Lights Monitor has a detector inserted in series with the trailer lights cable. The detector has a wireless connection to a display unit inside the vehicle which shows whether there is voltage on and current in each of the three trailer light circuits. The display consists of bi-colored LEDs which are off when the circuit is dead, Red for voltage only and Green for both voltage and current. Use of the monitor does not require any modifications to the car or trailer wiring.

If anyone is interested in building any of these devices I can provide a parts list, schematics, controller code, STL files for the enclosures, and more operational details. I do not have PCB layout files as I built mine using a proto board with wire wrap and solder connections.

Link to photo of Tow Altitude Recorder Units

https://drive.google.com/file/d/1tCA7B8A6xMUH8Ydso9i2KX4ivO_sTNo0/view?usp=sharing

Link to photo of Tow Plane Unit internal

https://drive.google.com/file/d/1DigdNxXg_Z8d1N-vDdFZCVPg8dYc3GB8/view?usp=sharing

[Quietpilot]

On Friday, December 18, 2020 at 10:16:46 AM UTC-6, wkau... wrote:
> Over the last two years, I've designed and built three Arduino based soaring related devices.. They are: 1) Tow Altitude Recorder with tow plane and ground units, 2) Cockpit Dual Battery Voltage & Temp Monitor, and 3)Trailer Lights Monitor.
>
> The Tow Altitude Recorder tow plane unit records the takeoff time and the tow plane release altitude. The release altitude is recorded automatically based on the highest altitude reached for the tow or manually using the Record Altitude button. The recorded launch time and tow altitude is transmitted to the ground unit once the tow plane is at or below 1000 ft AGL. The ground unit displays the launch time and altitude of the two previous tows but also allows the user to scroll through all tows for the day. Links to photos of the tow plane and ground units are included in this post. Both the tow plane and ground units use backlit sunlight readable LCD displays.
>
> The Cockpit Dual Battery Voltage & Temp Monitor measures and displays the avionics battery voltage and temperature inside the cockpit using a sunlight readable LCD display.
>
> The Trailer Lights Monitor has a detector inserted in series with the trailer lights cable. The detector has a wireless connection to a display unit inside the vehicle which shows whether there is the voltage on and current in each of the three trailer light circuits. The display consists of bi-colored LEDs which are off when the circuit is dead, Red for voltage only and Green for both voltage and current. Use of the monitor does not require any modifications to the car or trailer wiring.
>
> If anyone is interested in building any of these devices I can provide a parts list, schematics, controller code, STL files for the enclosures, and more operational details. I do not have PCB layout files as I built mine using a protoboard with wire wrap and solder connections.
>
> Link to photo of Tow Altitude Recorder Units
>
> https://drive.google.com/file/d/1tCA7B8A6xMUH8Ydso9i2KX4ivO_sTNo0/view?usp=sharing
>
> Link to photo of Tow Plane Unit internal
>
> https://drive.google.com/file/d/1DigdNxXg_Z8d1N-vDdFZCVPg8dYc3GB8/view?usp=sharing

I have been considering some open-source mesh devices as a project to collect similar data for the fleet to supplement unreadable/unreliable flight cards.

[Dan Marotta]

As a retired tow pilot I can tell you that often the glider pilot will
do a "soft release" and make no radio call. The tug continues happily
upwards until the pilot makes a periodic look into the mirror making the
recorded release height considerably higher than actual.

Maybe a lesson on poor technique, glider and tug...

On 12/18/20 9:16 AM, wrote:
> Over the last two years I've designed and built three Arduino based soaring related devices.. They are: 1) Tow Altitude Recorder with tow plane and ground units, 2) Cockpit Dual Battery Voltage & Temp Monitor, and 3)Trailer Lights Monitor.
>
> The Tow Altitude Recorder tow plane unit records the takeoff time and the tow plane release altitude. The release altitude is recorded automatically based on the highest altitude reached for the tow or manually using the Record Altitude button. The recorded launch time and tow altitude is transmitted to the ground unit once the tow plane is at or below 1000 ft AGL. The ground unit displays the launch time and altitude of the two previous tows but also allows the user to scroll through all tows for the day. Links to photos of the tow plane and ground units are included in this post. Both the tow plane and ground units use backlit sunlight readable LCD displays.
>
> The Cockpit Dual Battery Voltage & Temp Monitor measures and displays the avionics battery voltage and temperature inside the cockpit using a sunlight readable LCD display.
>
> The Trailer Lights Monitor has a detector inserted in series with the trailer lights cable. The detector has a wireless connection to a display unit inside the vehicle which shows whether there is voltage on and current in each of the three trailer light circuits. The display consists of bi-colored LEDs which are off when the circuit is dead, Red for voltage only and Green for both voltage and current. Use of the monitor does not require any modifications to the car or trailer wiring.
>
> If anyone is interested in building any of these devices I can provide a parts list, schematics, controller code, STL files for the enclosures, and more operational details. I do not have PCB layout files as I built mine using a proto board with wire wrap and solder connections.
>
> Link to photo of Tow Altitude Recorder Units
>
> https://drive.google.com/file/d/1tCA7B8A6xMUH8Ydso9i2KX4ivO_sTNo0/view?usp=sharing
>
> Link to photo of Tow Plane Unit internal
>
> https://drive.google.com/file/d/1DigdNxXg_Z8d1N-vDdFZCVPg8dYc3GB8/view?usp=sharing
>


--
Dan
5J

[Quietpilot]

On Friday, December 18, 2020 at 10:36:48 AM UTC-6, Dan Marotta wrote:
> As a retired tow pilot I can tell you that often the glider pilot will
> do a "soft release" and make no radio call. The tug continues happily
> upwards until the pilot makes a periodic look into the mirror making the
> recorded release height considerably higher than actual.
>
>Our Tow pilots report the same thing. and it wouldn't capture that except as compared to the glider logs and timestamps. Does the soft release have a measurable effect on wear of the TOST or Schweizer mechanism? for TOST overhaul it is limited to the # of release activations not flights if I recall. but that would be a different thread.

P9

[5Z]

On Friday, December 18, 2020 at 10:06:46 AM UTC-7, quietpilot wrote:
> >Our Tow pilots report the same thing. and it wouldn't capture that except as compared to the glider logs and timestamps.

Is there any way to measure the load on the tow hook? If a strain gauge could somehow be placed to measure the load, some smart logic could detect that a glider is no longer back there.
My guess is that a glider on to would always be putting a load of at least 40-50 lb when averaged over several seconds.

5Z

[Lauren Rezac]

On Friday, December 18, 2020 at 10:16:46 AM UTC-6, wrote:
> Over the last two years I've designed and built three Arduino based soaring related devices.. They are: 1) Tow Altitude Recorder with tow plane and ground units, 2) Cockpit Dual Battery Voltage & Temp Monitor, and 3)Trailer Lights Monitor.

Yes I am interested in the battery temp/voltage unit. (info on the other two might also be helpful:)

Thanks,

Lauren

[Eric Greenwell[_4_]]

5Z wrote on 12/18/2020 9:07 PM:
> On Friday, December 18, 2020 at 10:06:46 AM UTC-7, quietpilot wrote:
>>> Our Tow pilots report the same thing. and it wouldn't capture that except as compared to the glider logs and timestamps.
>
> Is there any way to measure the load on the tow hook? If a strain gauge could somehow be placed to measure the load, some smart logic could detect that a glider is no longer back there.
> My guess is that a glider on to would always be putting a load of at least 40-50 lb when averaged over several seconds.
>
> 5Z
>
Charge the glider pilot for the height the towplane went to, and next time he takes a tow,
he'll remember to say "off tow".

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[Martin Gregorie[_6_]]

On Fri, 18 Dec 2020 21:07:18 -0800, 5Z wrote:

> On Friday, December 18, 2020 at 10:06:46 AM UTC-7, quietpilot wrote:
>> >Our Tow pilots report the same thing. and it wouldn't capture that
>> >except as compared to the glider logs and timestamps.
>
> Is there any way to measure the load on the tow hook? If a strain gauge
> could somehow be placed to measure the load, some smart logic could
> detect that a glider is no longer back there.
> My guess is that a glider on to would always be putting a load of at
> least 40-50 lb when averaged over several seconds.
>
For level flight the load should be glider weight divided by glide ratio
at tow speed, but since the combination is climbing the load will be a
bit higher: by sin(glider weight) IIRC. When I calculated that I got
about 60 kg for a Std Libelle in a normal 65 kt climb behind a Robin
DR400.


--
--
Martin | martin at
Gregorie | gregorie dot org

[Eric Greenwell[_4_]]

wrote on 12/18/2020 8:16 AM:
> Over the last two years I've designed and built three Arduino based soaring related devices.. They are: 1) Tow Altitude Recorder with tow plane and ground units, 2) Cockpit Dual Battery Voltage & Temp Monitor, and 3)Trailer Lights Monitor.
>
Panasonic LiFe Batteries are now available with Bluetooth reporting of their status (volts,
current, state of charge, temperature) to a smartphone. I think a small, dedicated, panel
mounted display (BID - "battery information display") would be much more useful in-flight.

For batteries that don't have a built-in Bluetooth, you could develop a "BMS" (battery
measurement system) that mounts on each battery, and reports to the BID.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[[email protected]]

Eric,

The BID for the Panasonic LiFe batteries is a great idea for my next project.

Thanks,

Bill
On Saturday, December 19, 2020 at 8:57:50 AM UTC-5, Eric Greenwell wrote:
> wrote on 12/18/2020 8:16 AM:
> > Over the last two years I've designed and built three Arduino based soaring related devices.. They are: 1) Tow Altitude Recorder with tow plane and ground units, 2) Cockpit Dual Battery Voltage & Temp Monitor, and 3)Trailer Lights Monitor.
> >
> Panasonic LiFe Batteries are now available with Bluetooth reporting of their status (volts,
> current, state of charge, temperature) to a smartphone. I think a small, dedicated, panel
> mounted display (BID - "battery information display") would be much more useful in-flight.
>
> For batteries that don't have a built-in Bluetooth, you could develop a "BMS" (battery
> measurement system) that mounts on each battery, and reports to the BID.
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
> - "A Guide to Self-Launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[[email protected]]

Hi Lauren,

To keep the traffic down on this thread lets start an off line conversation to get you all the info and file and answer questions. Unfortunately I'm not able to reply directly to you. Do you have the same limitation? If so then please include your email on your next post.

Bill

On Saturday, December 19, 2020 at 8:06:21 AM UTC-5, Lauren Rezac wrote:
> On Friday, December 18, 2020 at 10:16:46 AM UTC-6, wrote:
> > Over the last two years I've designed and built three Arduino based soaring related devices.. They are: 1) Tow Altitude Recorder with tow plane and ground units, 2) Cockpit Dual Battery Voltage & Temp Monitor, and 3)Trailer Lights Monitor.
> Yes I am interested in the battery temp/voltage unit. (info on the other two might also be helpful:)
>
> Thanks,
>
> Lauren

[Dan Marotta]

On 12/19/20 6:49 AM, Martin Gregorie wrote:
> sin(glider weight)

How do you convert pounds, kilograms, stone, etc. to radians, degrees...?

--
Dan
5J

[Eric Greenwell[_4_]]

Dan Marotta wrote on 12/19/2020 7:55 AM:
> On 12/19/20 6:49 AM, Martin Gregorie wrote:
>> sin(glider weight)
>
> How do you convert pounds, kilograms, stone, etc. to radians, degrees...?
>
I think this is easier for the additional load: [(climb rate) x (glider weight)] / (tow speed)

No trigonometry required.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[Martin Gregorie[_6_]]

On Sat, 19 Dec 2020 08:55:02 -0700, Dan Marotta wrote:

> On 12/19/20 6:49 AM, Martin Gregorie wrote:
>> sin(glider weight)
>
> How do you convert pounds, kilograms, stone, etc. to radians,
> degrees...?

OK... glider_flying_weight * sin(climb angle)

This factor is needed because the tow rope is supporting a part of the
glider's flying weight - somewhere between zero in level flight to all of
it when a (jet-powered) tug is climbing vertically. At typical climb rate
on tow this amounts to a non-negligible fraction of the tension in the
rope.


--
--
Martin | martin at
Gregorie | gregorie dot org

[[email protected]]

OK guys, let's get this sorted out - and Yes, I will have donned my flame-proof suit by the time you're reading this!

A workable figure for the 'underlying' tension, (D + U), can be arrived at as follows: work out ...
D = (total weight of glider + pilot, etc.) / best glide ratio of that glider, and
U = (total weight of glider + pilot, etc.) / 10
Then add D and U to get the total 'underlying' tension (the steady-state tension, if you prefer).

The theory:
Tension in the aerotow rope in flight comprises 3 components:
D: the drag of the towed glider, dependent on its weight and its glide angle at towing speed
U: the "pulling Uphill" force, which is the weight of the glider x the sine of the angle of climb through the air (normally written as sin(angle))
J: the highly unpredictable and dynamically variable Jerk or "impulse" forces, resulting from bumps in the air, wiggles by the tug pilot, and proper (or otherwise) following behaviour of the glider pilot. These will also be scaled by other factors, such as elasticity and mass per unit length of the tow rope and (to a small extent in practical cases) by the respective total masses of tug and glider.

Note for D: normal towing speed is rarely far from best glide speed
Note for U: typical figures, in UK units:
- for a single-seater: 7kts climb at 70kts airspeed, giving the sine as 7/70 = 1/10
- for a two-seater: 6kts climb at 60kts airspeed, giving the sine as 6/60 = 1/10
- for better two-seaters: surprisingly little difference in climb angle, but ...
Note for J: this is potentially so variable that imprecision in assessment of D and U is unlikely to be of any concern.

Of course, a really powerful tug towing a really light glider will climb more steeply, so 10 may not be appropriate as the divisor in U.
If determining the sine in your own case, you must use identical units for airspeed and rate of climb - any density correction you apply to airspeed must also be applied to rate of climb. Some varios may give you true rates of climb, but the ASI will not give you true airspeed!
Note that extra climb rate caused by flying through lift does not affect the geometry, so does not affect the 'underlying' tension. It may well have an effect on variability of J - particularly in gusty thermals.

Martin's explanation was about right, in principle, but wrong in that the 'Uphill' component is significantly larger that the 'Drag' component for any practical glider (as opposed to hang-glider).

Eric wrote "No trigonometry required." But that *is* trigonometry - just without the frightening name!

Some may think that I have been random in my use of "mass" and "weight" - but no, barring slip-ups, and bearing in mind that it's late here!

More detailed explanation could be given, but are you still awake? Do you still have the will to live?
Happy Christmas, J.

[Mark Mocho]

Several years ago, one of our more "scientifically" inclined tow pilots rigged up a strain gauge at the tow hook and a laptop in the Pawnee cockpit to try to record loads and forces on the rope. I don't recall the actual numbers for my Pegasus, but the "scatter" in the data rendered the information virtually unusable. The "J" factor referenced above as the glider and tow plane encountered turbulence, reactions to control movements and out-of-position and/or uncoordinated flight made the load on the rope go from zero (slack line) to the weight of the glider. And it did it in such random steps that you couldn't make any sense of it. Maybe a more sophisticated system with more controlled conditions (i.e., smooth air) might reveal relevant results, but based on that one test, (as well as the data from several other tows with other gliders), I doubt any really usable information can be gleaned. The tow plane, tow rope and glider are in a very dynamic situation that is tough to quantify accurately. Good luck, as it would be interesting to see tests with better results.

[Eric Greenwell[_4_]]

Mark Mocho wrote on 12/19/2020 3:20 PM:
> Several years ago, one of our more "scientifically" inclined tow pilots rigged up a strain gauge at the tow hook and a laptop in the Pawnee cockpit to try to record loads and forces on the rope. I don't recall the actual numbers for my Pegasus, but the "scatter" in the data rendered the information virtually unusable. The "J" factor referenced above as the glider and tow plane encountered turbulence, reactions to control movements and out-of-position and/or uncoordinated flight made the load on the rope go from zero (slack line) to the weight of the glider. And it did it in such random steps that you couldn't make any sense of it. Maybe a more sophisticated system with more controlled conditions (i.e., smooth air) might reveal relevant results, but based on that one test, (as well as the data from several other tows with other gliders), I doubt any really usable information can be gleaned. The tow plane, tow rope and glider are in a very dynamic situation that is tough to quantify accurately. Good luck, as it would be interesting to see tests with better results.
>
As we all know, tow ropes do not break in steady flight! It's dynamic loads from turbulence and
piloting that put the peak loads on the rope; nonetheless, the average load (say, over 1
minute) will be close to the simple physics of lifting the weight of the glider at the rate of
climb. That number doesn't have much value in our operational choices, I think.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[Martin Gregorie[_6_]]

On Sat, 19 Dec 2020 16:24:01 -0800, Eric Greenwell wrote:

> As we all know, tow ropes do not break in steady flight! It's dynamic
> loads from turbulence and piloting that put the peak loads on the rope;
> nonetheless, the average load (say, over 1 minute) will be close to the
> simple physics of lifting the weight of the glider at the rate of climb.
> That number doesn't have much value in our operational choices, I think.
>
Yep. I only made an attempt at calculating it a while back because I was
curious about the tension in the tow rope under during normal operating
conditions.

I think there are other towing factors that are probably more important
to understand. For instance, the aerodynamics of towing our gliders with
our typical tow planes are quite different from those of the majority of
military glider tows because almost for virtually all military towing the
tow plane has a bigger wingspan than the glider. This was the case for
all British and US operations in WW2 and for most German towing too.

In fact, the only cases I've found where the military glider was bigger
span than the tug was the ME 321 Gigant (the Gigant was bigger than its
He-111Z towplane) and the DFS 230 when it was being towed by a BF-109 or
Bf-110.

Conversely the only civilian gliders I'm aware of that are smaller than
their towplane are Perlan 2 when the Grob G520 Egrett is towing it
and an SGS 1-26 behind a Piper Cub.

This can matter, because if the glider is smaller than its tug, its
entire wing is operating in the downwash from the tug's wing, while if
the glider is bigger than its tug, then, while the inner part of its wing
is in the downwash behind the tug's wing, the outer parts of its wing
project through the tug's tip turbulence and into the upwash created by
the outer parts of the tug's tip vortex and may well give an tendency for
the glider to tip stall if the tow speed is too slow.


--
--
Martin | martin at
Gregorie | gregorie dot org

[Eric Greenwell[_4_]]

Martin Gregorie wrote on 12/19/2020 6:52 PM:
> On Sat, 19 Dec 2020 16:24:01 -0800, Eric Greenwell wrote:
>
>> As we all know, tow ropes do not break in steady flight! It's dynamic
>> loads from turbulence and piloting that put the peak loads on the rope;
>> nonetheless, the average load (say, over 1 minute) will be close to the
>> simple physics of lifting the weight of the glider at the rate of climb.
>> That number doesn't have much value in our operational choices, I think.
>>
> Yep. I only made an attempt at calculating it a while back because I was
> curious about the tension in the tow rope under during normal operating
> conditions.
>
> I think there are other towing factors that are probably more important
> to understand. For instance, the aerodynamics of towing our gliders with
> our typical tow planes are quite different from those of the majority of
> military glider tows because almost for virtually all military towing the
> tow plane has a bigger wingspan than the glider. This was the case for
> all British and US operations in WW2 and for most German towing too.
>
> In fact, the only cases I've found where the military glider was bigger
> span than the tug was the ME 321 Gigant (the Gigant was bigger than its
> He-111Z towplane) and the DFS 230 when it was being towed by a BF-109 or
> Bf-110.
>
> Conversely the only civilian gliders I'm aware of that are smaller than
> their towplane are Perlan 2 when the Grob G520 Egrett is towing it
> and an SGS 1-26 behind a Piper Cub.
>
> This can matter, because if the glider is smaller than its tug, its
> entire wing is operating in the downwash from the tug's wing, while if
> the glider is bigger than its tug, then, while the inner part of its wing
> is in the downwash behind the tug's wing, the outer parts of its wing
> project through the tug's tip turbulence and into the upwash created by
> the outer parts of the tug's tip vortex and may well give an tendency for
> the glider to tip stall if the tow speed is too slow.

Doesn't the majority of the wash or downflow from the wing pass under the glider if it tows at
the same altitude as the tug? For example, I used to demonstrate the ease of positioning behind
the towplane to students by banking to left until the glider was way off center line, and I
never noticed any significant difference in the airflow from center to far out to the left.
This was with a 200' long towrope; perhaps, with a much shorter rope, the experience would be a
lot different.


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[Lauren Rezac]

On Saturday, December 19, 2020 at 8:42:08 AM UTC-6, wrote:
> Hi Lauren,
>
> To keep the traffic down on this thread lets start an off line conversation to get you all the info and file and answer questions. Unfortunately I'm not able to reply directly to you. Do you have the same limitation? If so then please include your email on your next post.
>
> Bill
> On Saturday, December 19, 2020 at 8:06:21 AM UTC-5, Lauren Rezac wrote:
> > On Friday, December 18, 2020 at 10:16:46 AM UTC-6, wrote:
> > > Over the last two years I've designed and built three Arduino based soaring related devices.. They are: 1) Tow Altitude Recorder with tow plane and ground units, 2) Cockpit Dual Battery Voltage & Temp Monitor, and 3)Trailer Lights Monitor.
> > Yes I am interested in the battery temp/voltage unit. (info on the other two might also be helpful:)
> >
> > Thanks,
> >
> > Lauren

Bill,

It is



Thanks,

Lauren Rezac

[RR]

Its all vary admirable that you are trying to calulate the nominal load while under tow, but it is not needed for the task at hand. You just need to know when it is non zero. A simple push button switch such that when the cable is under load it pushes on the switch. Design a link that come in contact under load. All the load goes to the link, and the switch detects that it is closed. A light spring seperates the link to open the contact with an empty rope. The monitor sees that the link is open and if open long enough (longest conceivable slack rope duration) and records the hight when it first went slack.

All that said, Eric's human factors solution (don't do soft releases, or say "thanks" on the radio) will avoid over charge.

[Lauren Rezac]

On Sunday, December 20, 2020 at 6:46:35 AM UTC-6, Lauren Rezac wrote:
> On Saturday, December 19, 2020 at 8:42:08 AM UTC-6, wrote:
> > Hi Lauren,
> >
> > To keep the traffic down on this thread lets start an off line conversation to get you all the info and file and answer questions. Unfortunately I'm not able to reply directly to you. Do you have the same limitation? If so then please include your email on your next post.
> >
> > Bill
> > On Saturday, December 19, 2020 at 8:06:21 AM UTC-5, Lauren Rezac wrote:
> > > On Friday, December 18, 2020 at 10:16:46 AM UTC-6, wrote:
> > > > Over the last two years I've designed and built three Arduino based soaring related devices.. They are: 1) Tow Altitude Recorder with tow plane and ground units, 2) Cockpit Dual Battery Voltage & Temp Monitor, and 3)Trailer Lights Monitor.
> > > Yes I am interested in the battery temp/voltage unit. (info on the other two might also be helpful:)
> > >
> > > Thanks,
> > >
> > > Lauren
> Bill,
>
> It is
>
>
>
> Thanks,
>
> Lauren Rezac
Bill,

Well that's interesting. It seem to remove all reference to email addresses. So lets try this a different way.

rezac6205

is the first part of the email then the at and comcast.net

Thanks,

Lauren

[Martin Gregorie[_6_]]

On Sat, 19 Dec 2020 20:22:36 -0800, Eric Greenwell wrote:

> Doesn't the majority of the wash or downflow from the wing pass under
> the glider if it tows at the same altitude as the tug?
>
Thats definitely the case for a narrow layer containing propwash and
turbulence coming off the tug wing: quite obvious when you hit it, but
there's a general downflow above and below that turbulent sheet and a
matching upflow beyond the tug wingtips which can be seen in both flow
visualizations and, in some cases, in photos of aircraft flying in foggy
conditions which show the upflow extending out beyond the wingtips to at
least half of each wing semi-span. After all, wing lift is essentially
due to momentum transfer: a mass of air with a momentum equivalent to the
aircraft weight is being deflected downward by the wings, so this air
mass must occupy a fairly large volume below and behind the aircraft.

I still have vivid memories of going to Chobham Common for a spot of
model flying on a calm day with a solid, cloud base at 1000-1500 ft. The
road we were on was directly along the Heathrow approach path and we were
heading west, away from Heathrow. Suddenly a 747 dropped out of the
overcast ahead of us with flaps and wheels down. Its wing was scooping
off the bottom of the cloud layer and hurling it downwards, making the
downflow clearly visible under its wing. It must have extended down
20-25% of the wingspan, so was very clearly visible: looking at it was
like seeing the Niagara Falls streaming down below the wing, making it
quite obvious that this downflow was supporting 180 tons of aircraft.

> For example, I
> used to demonstrate the ease of positioning behind the towplane to
> students by banking to left until the glider was way off center line,
> and I never noticed any significant difference in the airflow from
> center to far out to the left. This was with a 200' long towrope;
> perhaps, with a much shorter rope, the experience would be a lot
> different.
>
Yes, but that's in a fairly lightly loaded training glider. Some high
span competition types, e.g a JS-1C when fully ballasted, need a high tow
speed to avoid tip stalling. I've seen an absolute minimum tow speed of
77 kts quoted for a fully ballasted JS-1C. It seems likely that this is
at least partly due to the change in incident airflow along the wingspan
from the downflowing field behind the tug to the upflowing field which
extends much further out than its wingtips and immediate tip vortex. The
effect is to put the glider's tips at a higher AOA than the root, thus
cancelling the effect of any built-in washout in the wing.


--
--
Martin | martin at
Gregorie | gregorie dot org

[Eric Greenwell[_4_]]

Lauren Rezac wrote on 12/20/2020 4:51 AM:
> On Sunday, December 20, 2020 at 6:46:35 AM UTC-6, Lauren Rezac wrote:
>> On Saturday, December 19, 2020 at 8:42:08 AM UTC-6, wrote:
>>> Hi Lauren,
>>>
>>> To keep the traffic down on this thread lets start an off line conversation to get you all the info and file and answer questions. Unfortunately I'm not able to reply directly to you. Do you have the same limitation? If so then please include your email on your next post.
>>>
>>> Bill
>>> On Saturday, December 19, 2020 at 8:06:21 AM UTC-5, Lauren Rezac wrote:
>>>> On Friday, December 18, 2020 at 10:16:46 AM UTC-6, wrote:
>>>>> Over the last two years I've designed and built three Arduino based soaring related devices.. They are: 1) Tow Altitude Recorder with tow plane and ground units, 2) Cockpit Dual Battery Voltage & Temp Monitor, and 3)Trailer Lights Monitor.
>>>> Yes I am interested in the battery temp/voltage unit. (info on the other two might also be helpful:)
>>>>
>>>> Thanks,
>>>>
>>>> Lauren
>> Bill,
>>
>> It is
>>
>>
>>
>> Thanks,
>>
>> Lauren Rezac
> Bill,
>
> Well that's interesting. It seem to remove all reference to email addresses. So lets try this a different way.
>
> rezac6205
>
> is the first part of the email then the at and comcast.net
>
> Thanks,
>
> Lauren
>
I get RAS via emails, and they always include the poster's email address in the header, and
your email address is in the body in your reply. Now I'm curious: do you see your full email
address here:

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[Moshe Braner]

On 12/20/2020 9:04 AM, Eric Greenwell wrote:
> Lauren Rezac wrote on 12/20/2020 4:51 AM:
>> On Sunday, December 20, 2020 at 6:46:35 AM UTC-6, Lauren Rezac wrote:
>>> On Saturday, December 19, 2020 at 8:42:08 AM UTC-6,
>>> wrote:
>>>> Hi Lauren,
>>>>
>>>> To keep the traffic down on this thread lets start an off line
>>>> conversation to get you all the info and file and answer questions.
>>>> Unfortunately I'm not able to reply directly to you. Do you have the
>>>> same limitation? If so then please include your email on your next
>>>> post.
>>>>
>>>> Bill
>>>> On Saturday, December 19, 2020 at 8:06:21 AM UTC-5, Lauren Rezac wrote:
>>>>> On Friday, December 18, 2020 at 10:16:46 AM UTC-6,
>>>>> wrote:
>>>>>> Over the last two years I've designed and built three Arduino
>>>>>> based soaring related devices.. They are: 1) Tow Altitude Recorder
>>>>>> with tow plane and ground units, 2) Cockpit Dual Battery Voltage &
>>>>>> Temp Monitor, and 3)Trailer Lights Monitor.
>>>>> Yes I am interested in the battery temp/voltage unit. (info on the
>>>>> other two might also be helpful:)
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Lauren
>>> Bill,
>>>
>>> It is
>>>
>>>
>>>
>>> Thanks,
>>>
>>> Lauren Rezac
>> Bill,
>>
>> Â* Well that's interesting. It seem to remove all reference to email
>> addresses. So lets try this a different way.
>>
>> rezac6205
>>
>> is the first part of the email then the at and comcast.net
>>
>> Thanks,
>>
>> Lauren
>>
> I get RAS via emails, and they always include the poster's email address
> in the header, and your email address is in the body in your reply. Now
> I'm curious: do you see your full email address here:
>

If you read RAS through the Google Groups web site it usually masks part
of any email address. I used to access RAS that way, but after they
switched to their new dumbed down format (lacking reply-to-author-only)
I switched to using Mozilla Thunderbird reading the posts via
eternal-september. Another option for reading (not posting?) via a web
browser is here:
https://rec.aviation.soaring.narkive.com/

[John Galloway[_2_]]

On Sunday, 20 December 2020 at 14:01:25 UTC, Martin Gregorie wrote:
> On Sat, 19 Dec 2020 20:22:36 -0800, Eric Greenwell wrote:
>
> > Doesn't the majority of the wash or downflow from the wing pass under
> > the glider if it tows at the same altitude as the tug?
> >
> Thats definitely the case for a narrow layer containing propwash and
> turbulence coming off the tug wing: quite obvious when you hit it, but
> there's a general downflow above and below that turbulent sheet and a
> matching upflow beyond the tug wingtips which can be seen in both flow
> visualizations and, in some cases, in photos of aircraft flying in foggy
> conditions which show the upflow extending out beyond the wingtips to at
> least half of each wing semi-span. After all, wing lift is essentially
> due to momentum transfer: a mass of air with a momentum equivalent to the
> aircraft weight is being deflected downward by the wings, so this air
> mass must occupy a fairly large volume below and behind the aircraft.
>
> I still have vivid memories of going to Chobham Common for a spot of
> model flying on a calm day with a solid, cloud base at 1000-1500 ft. The
> road we were on was directly along the Heathrow approach path and we were
> heading west, away from Heathrow. Suddenly a 747 dropped out of the
> overcast ahead of us with flaps and wheels down. Its wing was scooping
> off the bottom of the cloud layer and hurling it downwards, making the
> downflow clearly visible under its wing. It must have extended down
> 20-25% of the wingspan, so was very clearly visible: looking at it was
> like seeing the Niagara Falls streaming down below the wing, making it
> quite obvious that this downflow was supporting 180 tons of aircraft.
> > For example, I
> > used to demonstrate the ease of positioning behind the towplane to
> > students by banking to left until the glider was way off center line,
> > and I never noticed any significant difference in the airflow from
> > center to far out to the left. This was with a 200' long towrope;
> > perhaps, with a much shorter rope, the experience would be a lot
> > different.
> >
> Yes, but that's in a fairly lightly loaded training glider. Some high
> span competition types, e.g a JS-1C when fully ballasted, need a high tow
> speed to avoid tip stalling. I've seen an absolute minimum tow speed of
> 77 kts quoted for a fully ballasted JS-1C. It seems likely that this is
> at least partly due to the change in incident airflow along the wingspan
> from the downflowing field behind the tug to the upflowing field which
> extends much further out than its wingtips and immediate tip vortex. The
> effect is to put the glider's tips at a higher AOA than the root, thus
> cancelling the effect of any built-in washout in the wing.
> --
> --
> Martin | martin at
> Gregorie | gregorie dot org

I agree with Martin's explanation. To my mind the fullest account of the issues towing very high wing-loading long span gliders is by Aldo Cernezzi in the Jan-Feb issue of Gliding International. The article is slightly misleadingly titled "The Creation of a Vortex". As the ex-owner of a JS1c 21m who had just launched in it before a fatal towing accident in another 21m JS1c my mind became very concentrated on this issue. I subsequently never launched it fully ballasted in 21m mode without getting a direct confirmation from the tow pilot that the minimum speed would be 75 knots. Not least because the ASIs in many tug planes over-read in flight as they don't use proper statics.

[John Galloway[_2_]]

On Sunday, 20 December 2020 at 16:52:39 UTC, John Galloway wrote:
> On Sunday, 20 December 2020 at 14:01:25 UTC, Martin Gregorie wrote:
> > On Sat, 19 Dec 2020 20:22:36 -0800, Eric Greenwell wrote:
> >
> > > Doesn't the majority of the wash or downflow from the wing pass under
> > > the glider if it tows at the same altitude as the tug?
> > >
> > Thats definitely the case for a narrow layer containing propwash and
> > turbulence coming off the tug wing: quite obvious when you hit it, but
> > there's a general downflow above and below that turbulent sheet and a
> > matching upflow beyond the tug wingtips which can be seen in both flow
> > visualizations and, in some cases, in photos of aircraft flying in foggy
> > conditions which show the upflow extending out beyond the wingtips to at
> > least half of each wing semi-span. After all, wing lift is essentially
> > due to momentum transfer: a mass of air with a momentum equivalent to the
> > aircraft weight is being deflected downward by the wings, so this air
> > mass must occupy a fairly large volume below and behind the aircraft.
> >
> > I still have vivid memories of going to Chobham Common for a spot of
> > model flying on a calm day with a solid, cloud base at 1000-1500 ft. The
> > road we were on was directly along the Heathrow approach path and we were
> > heading west, away from Heathrow. Suddenly a 747 dropped out of the
> > overcast ahead of us with flaps and wheels down. Its wing was scooping
> > off the bottom of the cloud layer and hurling it downwards, making the
> > downflow clearly visible under its wing. It must have extended down
> > 20-25% of the wingspan, so was very clearly visible: looking at it was
> > like seeing the Niagara Falls streaming down below the wing, making it
> > quite obvious that this downflow was supporting 180 tons of aircraft.
> > > For example, I
> > > used to demonstrate the ease of positioning behind the towplane to
> > > students by banking to left until the glider was way off center line,
> > > and I never noticed any significant difference in the airflow from
> > > center to far out to the left. This was with a 200' long towrope;
> > > perhaps, with a much shorter rope, the experience would be a lot
> > > different.
> > >
> > Yes, but that's in a fairly lightly loaded training glider. Some high
> > span competition types, e.g a JS-1C when fully ballasted, need a high tow
> > speed to avoid tip stalling. I've seen an absolute minimum tow speed of
> > 77 kts quoted for a fully ballasted JS-1C. It seems likely that this is
> > at least partly due to the change in incident airflow along the wingspan
> > from the downflowing field behind the tug to the upflowing field which
> > extends much further out than its wingtips and immediate tip vortex. The
> > effect is to put the glider's tips at a higher AOA than the root, thus
> > cancelling the effect of any built-in washout in the wing.
> > --
> > --
> > Martin | martin at
> > Gregorie | gregorie dot org
> I agree with Martin's explanation. To my mind the fullest account of the issues towing very high wing-loading long span gliders is by Aldo Cernezzi in the Jan-Feb issue of Gliding International. The article is slightly misleadingly titled "The Creation of a Vortex". As the ex-owner of a JS1c 21m who had just launched in it before a fatal towing accident in another 21m JS1c my mind became very concentrated on this issue. I subsequently never launched it fully ballasted in 21m mode without getting a direct confirmation from the tow pilot that the minimum speed would be 75 knots. Not least because the ASIs in many tug planes over-read in flight as they don't use proper statics.

To correct myself. The main article is called Poor Handling on Tow. The above mentioned article follows on from it.

[Eric Greenwell[_4_]]

John Galloway wrote on 12/20/2020 11:01 AM:
> On Sunday, 20 December 2020 at 16:52:39 UTC, John Galloway wrote:
>> On Sunday, 20 December 2020 at 14:01:25 UTC, Martin Gregorie wrote:
>>> On Sat, 19 Dec 2020 20:22:36 -0800, Eric Greenwell wrote:
>>>
>>>> Doesn't the majority of the wash or downflow from the wing pass under
>>>> the glider if it tows at the same altitude as the tug?
>>>>
>>> Thats definitely the case for a narrow layer containing propwash and
>>> turbulence coming off the tug wing: quite obvious when you hit it, but
>>> there's a general downflow above and below that turbulent sheet and a
>>> matching upflow beyond the tug wingtips which can be seen in both flow
>>> visualizations and, in some cases, in photos of aircraft flying in foggy
>>> conditions which show the upflow extending out beyond the wingtips to at
>>> least half of each wing semi-span. After all, wing lift is essentially
>>> due to momentum transfer: a mass of air with a momentum equivalent to the
>>> aircraft weight is being deflected downward by the wings, so this air
>>> mass must occupy a fairly large volume below and behind the aircraft.
>>>
>>> I still have vivid memories of going to Chobham Common for a spot of
>>> model flying on a calm day with a solid, cloud base at 1000-1500 ft. The
>>> road we were on was directly along the Heathrow approach path and we were
>>> heading west, away from Heathrow. Suddenly a 747 dropped out of the
>>> overcast ahead of us with flaps and wheels down. Its wing was scooping
>>> off the bottom of the cloud layer and hurling it downwards, making the
>>> downflow clearly visible under its wing. It must have extended down
>>> 20-25% of the wingspan, so was very clearly visible: looking at it was
>>> like seeing the Niagara Falls streaming down below the wing, making it
>>> quite obvious that this downflow was supporting 180 tons of aircraft.
>>>> For example, I
>>>> used to demonstrate the ease of positioning behind the towplane to
>>>> students by banking to left until the glider was way off center line,
>>>> and I never noticed any significant difference in the airflow from
>>>> center to far out to the left. This was with a 200' long towrope;
>>>> perhaps, with a much shorter rope, the experience would be a lot
>>>> different.
>>>>
>>> Yes, but that's in a fairly lightly loaded training glider. Some high
>>> span competition types, e.g a JS-1C when fully ballasted, need a high tow
>>> speed to avoid tip stalling. I've seen an absolute minimum tow speed of
>>> 77 kts quoted for a fully ballasted JS-1C. It seems likely that this is
>>> at least partly due to the change in incident airflow along the wingspan
>>> from the downflowing field behind the tug to the upflowing field which
>>> extends much further out than its wingtips and immediate tip vortex. The
>>> effect is to put the glider's tips at a higher AOA than the root, thus
>>> cancelling the effect of any built-in washout in the wing.
>>> --
>>> --
>>> Martin | martin at
>>> Gregorie | gregorie dot org
>> I agree with Martin's explanation. To my mind the fullest account of the issues towing very high wing-loading long span gliders is by Aldo Cernezzi in the Jan-Feb issue of Gliding International. The article is slightly misleadingly titled "The Creation of a Vortex". As the ex-owner of a JS1c 21m who had just launched in it before a fatal towing accident in another 21m JS1c my mind became very concentrated on this issue. I subsequently never launched it fully ballasted in 21m mode without getting a direct confirmation from the tow pilot that the minimum speed would be 75 knots. Not least because the ASIs in many tug planes over-read in flight as they don't use proper statics.
>
> To correct myself. The main article is called Poor Handling on Tow. The above mentioned article follows on from it.
>
Did all these accidents/incidents occur while the glider was at the altitude as the tow plane?
What was the length of the tow rope in use?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[Dave Nadler]

On 12/20/2020 9:01 AM, Martin Gregorie wrote:
> On Sat, 19 Dec 2020 20:22:36 -0800, Eric Greenwell wrote:
>
>> Doesn't the majority of the wash or downflow from the wing pass under
>> the glider if it tows at the same altitude as the tug?
>>
> Thats definitely the case for a narrow layer containing propwash and
> turbulence coming off the tug wing: quite obvious when you hit it, but
> there's a general downflow above and below that turbulent sheet and a
> matching upflow beyond the tug wingtips which can be seen in both flow
> visualizations and, in some cases, in photos of aircraft flying in foggy
> conditions which show the upflow extending out beyond the wingtips to at
> least half of each wing semi-span. After all, wing lift is essentially
> due to momentum transfer: a mass of air with a momentum equivalent to the
> aircraft weight is being deflected downward by the wings, so this air
> mass must occupy a fairly large volume below and behind the aircraft.
>
> I still have vivid memories of going to Chobham Common for a spot of
> model flying on a calm day with a solid, cloud base at 1000-1500 ft. The
> road we were on was directly along the Heathrow approach path and we were
> heading west, away from Heathrow. Suddenly a 747 dropped out of the
> overcast ahead of us with flaps and wheels down. Its wing was scooping
> off the bottom of the cloud layer and hurling it downwards, making the
> downflow clearly visible under its wing. It must have extended down
> 20-25% of the wingspan, so was very clearly visible: looking at it was
> like seeing the Niagara Falls streaming down below the wing, making it
> quite obvious that this downflow was supporting 180 tons of aircraft.
>
>> For example, I
>> used to demonstrate the ease of positioning behind the towplane to
>> students by banking to left until the glider was way off center line,
>> and I never noticed any significant difference in the airflow from
>> center to far out to the left. This was with a 200' long towrope;
>> perhaps, with a much shorter rope, the experience would be a lot
>> different.
>>
> Yes, but that's in a fairly lightly loaded training glider. Some high
> span competition types, e.g a JS-1C when fully ballasted, need a high tow
> speed to avoid tip stalling. I've seen an absolute minimum tow speed of
> 77 kts quoted for a fully ballasted JS-1C. It seems likely that this is
> at least partly due to the change in incident airflow along the wingspan
> from the downflowing field behind the tug to the upflowing field which
> extends much further out than its wingtips and immediate tip vortex. The
> effect is to put the glider's tips at a higher AOA than the root, thus
> cancelling the effect of any built-in washout in the wing.

See: https://www.youtube.com/watch?v=WIZWzvMu1dM from time 13:40
Hope that's clear,
Best Regards, Dave

[Marton KSz]

""If anyone is interested in building any of these devices I can provide a parts list, schematics, controller code, STL files for the enclosures, and more operational details. ""


Upload them to GitHub or Hackaday.io