Newbie help required!
Lets suppose I am on a shallow final glide, 60k out in my 40:1 ship, cruising at 60 knots. Recent thermals have been at least 5 knots and I am coming into some big lift. For the discussion rough air Vne is 100 knots.
What strength thermal should I take to increase finishing speed to Vne and how much (if any) time will this save me?
How do I estimate this at the time? What is the latest point on track to take such a thermal?

Thanks, Bagmaker

Doug Hoffman schrieb:
> bagmaker wrote:
>
>>Newbie help required!
>>Lets suppose I am on a shallow final glide, 60k out in my 40:1 ship,
>>cruising at 60 knots. Recent thermals have been at least 5 knots and I
>>am coming into some big lift. For the discussion rough air Vne is 100
>>knots.
>>What strength thermal should I take to increase finishing speed to Vne
>>and how much (if any) time will this save me?
>>How do I estimate this at the time? What is the latest point on track
>>to take such a thermal?
>
>
> Need to know sink rate at Vne, right? Also, 40:1 is at 60 knots?
>
> Regards,
>
> -Doug
>

As a guidance:
If your MC-Value for final glide is lower than the thermal-strenght you
encouter, use the thermal up to the altitude that allows you to continue your
final glide with the NEW MC-value.

Example:
Final glide with MC=1.0 m/s
New Thermal 2m/s.
You gain 300 additional meters of altitude to continue now at MC=2.0m/s to you
destination.

CU
Markus

Actually you want to glide back at the correct McCready
speed for the strength of the last thermal you use.
Climb just high enough to give yourself a reasonable
safety margin, for which you need a glide calculator
of some sort. If you are flying at 60 knots after using
5 knot thermals you are flying far too slowly for the
conditions (assuming that you are trying to race).
Did you mean that rough air Vne is 100 knots? This
sounds like a more reasonable inter thermal speed for
the conditions. I would suggest that you should take
any thermal that gives you at least a comfortable 5
knots climb rate.

Derek copeland


At 04:12 10 March 2006, Bagmaker wrote:
>
>Newbie help required!
>Lets suppose I am on a shallow final glide, 60k out
>in my 40:1 ship
>cruising at 60 knots. Recent thermals have been at
>least 5 knots and
>am coming into some big lift. For the discussion rough
>air Vne is 10
>knots.
>What strength thermal should I take to increase finishing
>speed to Vn
>and how much (if any) time will this save me?
>How do I estimate this at the time? What is the latest
>point on trac
>to take such a thermal?
>
>Thanks, Bagmake
>
>
>--
>bagmaker
>

This begs the question: If recent thermals have been at least 5 knots,
why on earth are you cruising at 60 knots? Sounds more like you missed
the last one and are low, searching for the "get home" thermal. Been
there done that!

Then, while climbing, set computer to achieved climb, and start final
glide when proper altitude is reached (plus safety alt, and taking
winds into account - that's why you pay the big bucks for the
computer!).

Rarely will final glide be started at Vne - the high speed final glides
are usually the result of either running into a lot of extra lift
during the final glide (lots of fun, that), or caused by burning off
the safety altitude when the field is made. Of course, if you insist
on topping off that 7 knot thermal 10 miles out...

So if you want to finish at VNE, add 1000' to field elevation - that
should allow accelerating to VNE for that nice crowd pleasing low pass.

Cheers,

Kirk
66

wrote:

> So if you want to finish at VNE, add 1000' to field elevation - that
> should allow accelerating to VNE for that nice crowd pleasing low pass.

OH! OH! Bad, Bad, Bad! You can't do those! No! No!! NO!!!

Haven't had that flame war in a while.

HTH ;-)
Shawn

Hmm, anybody read the AIM carefully lately? Especially the part where
the FAA defines a "low pass"?

Looks like the FAA actually condones low passes - and tells you how to
do them!

Perfectly legal, if done correctly and safely, of course.

Regardless of what a bunch of jealous old twirlybird curmudgeons would
want you to believe...

Now, 500' finishes at 1 mile - THOSE are dangerous!

<flame suit on> ;>)

Kirk
66

wrote:
> Hmm, anybody read the AIM carefully lately? Especially the part where
> the FAA defines a "low pass"?
>
> Looks like the FAA actually condones low passes - and tells you how to
> do them!

....as low approaches, in the context of go-arounds from practice
instrument procedures. [AIM 4-3-12]

If you think the FAA is defining/approving low passes by gliders at
uncontrolled airports, that is something we shouldn't wish for. It might
be hard to convince them that the 500' rule shouldn't apply.

I like low passes just fine -- those worms which are not used for bait
deserve a little warm-up -- but let's not stretch too far looking for
approval. You know what happens when you seek permission.


Jack

Jack, you are reading too much into the AIM - Instrument go-arounds are
given as an example only - not as the only authorized use.

Heck, a plain old go-around on short final for a cow on the runway fits
the example, too!

Or a flyby so the tower can see if the geardoors are flush.

The point is you don't have to land out of a approach.

If it isn't prohibited, it's OK, if done in compliance with the rules.

So yeah, don't buzz the ramp. But down the runway, back into the
pattern? Perfectly legal.

But I agree with not asking for permission - and it's just common sense
to pick the time and place carefully - not at the local part 141 flight
school airport on a busy Saturday afternoon, for example!

The problem is with people who should know better prohibiting
activities just because they think it is wrong, regardless of fact.

Kirk
66

This came about doing sims, I realise things can get a little different in real life!
I found that if I estimated my glide distance at a slow speed, from the top of a distant thermal WITH MC AT 0 -even though thermals are mc 5- my overall finishing speed would usually be higher than stopping during that slow final glide to top up and finish faster.
How would I estimate it all?
Bagger

bagmaker wrote:
> Newbie help required!
> Lets suppose I am on a shallow final glide, 60k out in my 40:1 ship,
> cruising at 60 knots. Recent thermals have been at least 5 knots and I
> am coming into some big lift. For the discussion rough air Vne is 100
> knots.

Best not to confuse "rough air" speeds with Vne, which is the "never
exceed" speed. The "rough air" limit (I'm not sure this is used any more
- only my very old gliders had it) is quite a bit lower, and the newer
gliders don't have it, but do state "maneuvering speed", lower yet.

And, practically speaking, you certainly don't want to be going Vne when
there are thermals bigger than 5 knots in your way! If the glider hangs
together, it will be a very rough ride.

> What strength thermal should I take to increase finishing speed to Vne

You need your gilder's polar to determine what strength thermal is
needed for any McCready speed determination - nothing else needed.

> and how much (if any) time will this save me?

It will save you time, but without the polar, your altitude above the
finish, and the distance to the finish, we can't give you a number.

> How do I estimate this at the time?

You don't have to estimate it. A chart of speed vs McCready settings is
made up ahead of time. The less thinking you have to do while flying,
the more time you can spend flying the glider.

What is the latest point on track
> to take such a thermal?

I'm guessing, but I'd say about where you need to stay in the thermal at
least one full turn to get high enough to use the 100 knot speed. Any
closer, and you'd waste time getting unneeded altitude.


--
Change "netto" to "net" to email me directly

Eric Greenwell - Washington State, USA

www.motorglider.org - Download "A Guide to Self-launching Sailplane
Operation"

Eric, regarding the rough air speed - I thought you
flew an ASH 26? If so the BGA datasheet (quoting the
'FAA Web') lists the rough air speed as 99 knots i.e
the same as the manoeuvring speed. For my 2005 Discus
2cT the speeds are both 103 knots. I think all gliders
have a rough air speed limit for conditions such as
'wave rotor, thunderclouds, visible whirlwinds or when
crossing mountain ridges' to quote my manual.

http://www.gliding.co.uk/bgainfo/technical/datasheets/ash26.pdf

Bagmaker - you seem analytically minded so have a look
at John Cochrane's excellent paper 'Just a Little Faster
Please'. The link won't post but if you Google +'john
cochrane' +soaring you will get his site.

John Galloway

At 06:36 11 March 2006, Eric Greenwell wrote:
>bagmaker wrote:
>> Newbie help required!
>> Lets suppose I am on a shallow final glide, 60k out
>>in my 40:1 ship,
>> cruising at 60 knots. Recent thermals have been at
>>least 5 knots and I
>> am coming into some big lift. For the discussion rough
>>air Vne is 100
>> knots.
>
>Best not to confuse 'rough air' speeds with Vne, which
>is the 'never
>exceed' speed. The 'rough air' limit (I'm not sure
>this is used any more
>- only my very old gliders had it) is quite a bit lower,
>and the newer
>gliders don't have it, but do state 'maneuvering speed',
>lower yet.
>
>And, practically speaking, you certainly don't want
>to be going Vne when
>there are thermals bigger than 5 knots in your way!
>If the glider hangs
>together, it will be a very rough ride.
>
>> What strength thermal should I take to increase finishing
>>speed to Vne
>
>You need your gilder's polar to determine what strength
>thermal is
>needed for any McCready speed determination - nothing
>else needed.
>
>> and how much (if any) time will this save me?
>
>It will save you time, but without the polar, your
>altitude above the
>finish, and the distance to the finish, we can't give
>you a number.
>
>> How do I estimate this at the time?
>
>You don't have to estimate it. A chart of speed vs
>McCready settings is
>made up ahead of time. The less thinking you have to
>do while flying,
>the more time you can spend flying the glider.
>
> What is the latest point on track
>> to take such a thermal?
>
>I'm guessing, but I'd say about where you need to stay
>in the thermal at
>least one full turn to get high enough to use the 100
>knot speed. Any
>closer, and you'd waste time getting unneeded altitude.
>
>
>--
>Change 'netto' to 'net' to email me directly
>
>Eric Greenwell - Washington State, USA
>
>www.motorglider.org - Download 'A Guide to Self-launching
>Sailplane
>Operation'

bagmaker wrote:

> Lets suppose I am on a shallow final glide, 60k out in my 40:1 ship,
> cruising at 60 knots. Recent thermals have been at least 5 knots and I
> am coming into some big lift. For the discussion rough air Vne is 100
> knots.
> What strength thermal should I take to increase finishing speed to Vne
> and how much (if any) time will this save me?

Assumptions:
1) 60 knots at curent altitude will get you there (just).
2) 60k is 60 nautical miiles(nm)
3) there is no wind - this keeps your example simpler
4) 40:1 is at 60 knots
5) glider sink rate at 100 knots is 6 ft/sec

So you know you will finish in 1 hour at 60 knots, current altitude.
At 100 knots, you will finish in 60nm(1 hr/100 nm) = .6 hr = 36
minutes.
But you need to know how long to climb so you can go 100 knots.
Your current altitude is 60nm/40 = 1.5 nm.
1.5nm(6000 ft/nm) = about 9,000 ft.
36min(60 sec/min) = 2,160 sec
2,160 sec(6 ft/sec) = about 13,000 ft of altitude needed.
This means you need to climb about 4,000 ft.
A 5 knot thermal will give you about 500 ft/min.
So it will take you 4,000ft(1min/500ft) = about 8 minutes to climb.
So total time is 8min + 36min = 44min, or 16 minutes faster than
1hour.

> How do I estimate this at the time?

I wouldn't. As others have indicated, use of a flight computer is the
best way to go.

Regards,

-Doug

I should point out that the above is a bit of an oversimplification in
that the distance travelled through the air will be greater than the
ground track distance. So it would take a bit longer than 1 hour to
glide 60 *ground* nm at an *airspeed* of 60 knots. Also, it would take
proportionally longer than 36 minutes to cover the same ground from a
4,000 ft higher altitude. A more rigorous calculation would account
for this.

Regards,

-Doug

At 15:36 11 March 2006, Doug Hoffman wrote:
>I should point out that the above is a bit of an oversimplificatio
>>n in
>that the distance travelled through the air will be
>greater than the
>ground track distance. So it would take a bit longer
>than 1 hour to
>glide 60 *ground* nm at an *airspeed* of 60 knots.
> Also, it would take
>proportionally longer than 36 minutes to cover the
>same ground from a
>4,000 ft higher altitude. A more rigorous calculation
>would account
>for this.


0018 and .0022 seconds longer respectively - I think
we can safely call that false precision.

9B

At 15:36 11 March 2006, Doug Hoffman wrote:
>I should point out that the above is a bit of an oversimplificatio
>>n in
>that the distance travelled through the air will be
>greater than the
>ground track distance. So it would take a bit longer
>than 1 hour to
>glide 60 *ground* nm at an *airspeed* of 60 knots.
> Also, it would take
>proportionally longer than 36 minutes to cover the
>same ground from a
>4,000 ft higher altitude. A more rigorous calculation
>would account
>for this.


0018 and .0022 minutes longer respectively - I think
we can safely call that false precision.

9B

John Galloway wrote:
> Eric, regarding the rough air speed - I thought you
> flew an ASH 26? If so the BGA datasheet (quoting the
> 'FAA Web') lists the rough air speed as 99 knots i.e
> the same as the manoeuvring speed. For my 2005 Discus
> 2cT the speeds are both 103 knots. I think all gliders
> have a rough air speed limit for conditions such as
> 'wave rotor, thunderclouds, visible whirlwinds or when
> crossing mountain ridges' to quote my manual.
>
You're right, John - I should've checked my manual. Does anyone know how
the Rough Air limit is determined? Is it always the same as the
maneuvering speed limit in gliders? It's been a long time, but I recall
the rough air limit being different (significantly higher) than the
maneuvering speed for my Std Cirrus.

--
Change "netto" to "net" to email me directly

Eric Greenwell - Washington State, USA

www.motorglider.org - Download "A Guide to Self-launching Sailplane
Operation"

In article >,
Eric Greenwell > wrote:

> You're right, John - I should've checked my manual. Does anyone know how
> the Rough Air limit is determined? Is it always the same as the
> maneuvering speed limit in gliders?

No it's not. Our Janus, for example, has maneuvering at 92 knots, but
both rough air and Vne at 119 knots.

--
Bruce | 41.1670S | \ spoken | -+-
Hoult | 174.8263E | /\ here. | ----------O----------

Yes 119 knots for both rough air and VNE for the Standard
Cirrus with a manouevring speed of only 81knots.

A quick scout through the BGA datasheets seems to show
a trend that for modern single seaters the rough air
and manouevring speeds are the same but for some older
singles and current deep spar two seaters the rough
air is higher. I don't know how the speeds are determined.

http://www.gliding.co.uk/bgainfo/technical/datasheets.htm




At 16:30 11 March 2006, Eric Greenwell wrote:
>John Galloway wrote:
>> Eric, regarding the rough air speed - I thought you
>> flew an ASH 26? If so the BGA datasheet (quoting
>>the
>> 'FAA Web') lists the rough air speed as 99 knots i.e
>> the same as the manoeuvring speed. For my 2005 Discus
>> 2cT the speeds are both 103 knots. I think all gliders
>> have a rough air speed limit for conditions such as
>> 'wave rotor, thunderclouds, visible whirlwinds or
>>when
>> crossing mountain ridges' to quote my manual.
>>
>You're right, John - I should've checked my manual.
>Does anyone know how
>the Rough Air limit is determined? Is it always the
>same as the
>maneuvering speed limit in gliders? It's been a long
>time, but I recall
>the rough air limit being different (significantly
>higher) than the
>maneuvering speed for my Std Cirrus.
>
>--
>Change 'netto' to 'net' to email me directly
>
>Eric Greenwell - Washington State, USA
>
>www.motorglider.org - Download 'A Guide to Self-launching
>Sailplane
>Operation'
>

This is the basic method to set maneuvering speed:

The Maneuvering Speed is the minimum speed at which the wing can
produce lift equal to the design load limit. (in positive G's) Below
this speed the wing can not produce enough lift to overstress the
aircraft, no matter what angle of attack is used.

Rough air speed is generally set so that a certain limit of turbulence
will not over stress the aircraft.

Todd
3S

John Galloway wrote:

> A quick scout through the BGA datasheets seems to show
> a trend that for modern single seaters the rough air
> and manouevring speeds are the same

Yes, but I don't believe it's really for technical reasons. I rather
suspect that the manufactorer defines it deliberately that way to keep
things simple for the pilot. (Quick test: Do you know whether the green
arc defines maneuvring speed or rough air speed?)

Stefan

toad wrote:
> This is the basic method to set maneuvering speed:
>
> The Maneuvering Speed is the minimum speed at which the wing can
> produce lift equal to the design load limit. (in positive G's) Below
> this speed the wing can not produce enough lift to overstress the
> aircraft, no matter what angle of attack is used.

Maneuvering speed assumes max gross weight. If you're flying lighter
the wing can make enough lift to break.

Shawn

In article >,
Stefan > wrote:

> John Galloway wrote:
>
> > A quick scout through the BGA datasheets seems to show
> > a trend that for modern single seaters the rough air
> > and manouevring speeds are the same
>
> Yes, but I don't believe it's really for technical reasons. I rather
> suspect that the manufactorer defines it deliberately that way to keep
> things simple for the pilot. (Quick test: Do you know whether the green
> arc defines maneuvring speed or rough air speed?)

Manouevring.

Rough air places lower loads on a structure than do extreme control
deflections, so rough air speed will always be the same as or higher
than manouevring speed, never lower.

--
Bruce | 41.1670S | \ spoken | -+-
Hoult | 174.8263E | /\ here. | ----------O----------

John Galloway wrote:
> Yes 119 knots for both rough air and VNE for the Standard
> Cirrus with a manouevring speed of only 81knots.

I notice the Hornet has it reversed: Rough air = 75 knots; maneuvering =
81. It's hard to believe the Hornet might be in trouble at 76 knots and
the Cirrus could blast on past at 119 knots!

> A quick scout through the BGA datasheets seems to show
> a trend that for modern single seaters the rough air
> and manouevring speeds are the same but for some older
> singles and current deep spar two seaters the rough
> air is higher. I don't know how the speeds are determined.
>
> http://www.gliding.co.uk/bgainfo/technical/datasheets.htm




--
Change "netto" to "net" to email me directly

Eric Greenwell - Washington State, USA

www.motorglider.org - Download "A Guide to Self-launching Sailplane
Operation"

Shawn wrote:
> toad wrote:
> > This is the basic method to set maneuvering speed:
> >
> > The Maneuvering Speed is the minimum speed at which the wing can
> > produce lift equal to the design load limit. (in positive G's) Below
> > this speed the wing can not produce enough lift to overstress the
> > aircraft, no matter what angle of attack is used.
>
> Maneuvering speed assumes max gross weight. If you're flying lighter
> the wing can make enough lift to break.
>
> Shawn

This is true, at lighter weights the maneuvering speed goes down, since
the airframe is only strong enough for X g's.

Toad

Bruce Hoult wrote:
> In article >,
> Eric Greenwell > wrote:
>
>> You're right, John - I should've checked my manual. Does anyone know how
>> the Rough Air limit is determined? Is it always the same as the
>> maneuvering speed limit in gliders?
>
> No it's not. Our Janus, for example, has maneuvering at 92 knots, but
> both rough air and Vne at 119 knots.

That seems to suggest the pilot can damage the glider, but turbulence
cannot. Perhaps that's not unreasonable, given the very low Vne,
suggesting the flutter issues were not handled as well as the airframe
strength.

--
Change "netto" to "net" to email me directly

Eric Greenwell - Washington State, USA

www.motorglider.org - Download "A Guide to Self-launching Sailplane
Operation"

Shawn wrote:
> toad wrote:
>> This is the basic method to set maneuvering speed:
>>
>> The Maneuvering Speed is the minimum speed at which the wing can
>> produce lift equal to the design load limit. (in positive G's) Below
>> this speed the wing can not produce enough lift to overstress the
>> aircraft, no matter what angle of attack is used.
>
> Maneuvering speed assumes max gross weight. If you're flying lighter
> the wing can make enough lift to break.

So, for gliders, the flight manual figure only applies if you are
carrying full water ballast, and you are supposed to guess at what is
when the glider is unballasted?

--
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Eric Greenwell - Washington State, USA

www.motorglider.org - Download "A Guide to Self-launching Sailplane
Operation"

Eric Greenwell wrote:
> Shawn wrote:
>
>> toad wrote:
>>
>>> This is the basic method to set maneuvering speed:
>>>
>>> The Maneuvering Speed is the minimum speed at which the wing can
>>> produce lift equal to the design load limit. (in positive G's) Below
>>> this speed the wing can not produce enough lift to overstress the
>>> aircraft, no matter what angle of attack is used.
>>
>>
>> Maneuvering speed assumes max gross weight. If you're flying lighter
>> the wing can make enough lift to break.
>
>
> So, for gliders, the flight manual figure only applies if you are
> carrying full water ballast, and you are supposed to guess at what is
> when the glider is unballasted?

No, just calculate it by taking the square root of the mass/max gross
and multiply that by Va, in the cockpit, in rotor, while dropping below
glide to the nearest safe field.
Simple!

The physics argument for Va decreasing with lower mass makes sense.
However, the legal argument for what maneuvering speed should be used
would support the notion of a constant Va at all weights.

Shawn

Andy Blackburn wrote:

> 0018 and .0022 seconds longer respectively - I think
> we can safely call that false precision.

Hi Andy,

Yes. Of course you are right. Thanks for running the check.

Regards,

-Doug

Are you sure they would not use a worst case scenario?

Paul

Shawn wrote:

>
> Maneuvering speed assumes max gross weight. If you're flying lighter
> the wing can make enough lift to break.
>
> Shawn

Are you sure they would not use a worst case scenario?

Paul

Shawn wrote:

>
> Maneuvering speed assumes max gross weight. If you're flying lighter
> the wing can make enough lift to break.
>
> Shawn

> No, just calculate it by taking the square root of the mass/max gross
> and multiply that by Va, in the cockpit, in rotor, while dropping below
> glide to the nearest safe field.
> Simple!

LOL!

Of course, you could also do it safely on the ground when you first get
the glider. Or simply subtract about 15 - 20 knots as a "rule of thumb".

Tony V.

The manufacturor would probably state the weight condition that Va
applies for, ballasted or dry. I would expect that the Va was stated
for dry.

The wing structure would not break at a lower Va due to lower weights.
It's structure like the pilot seat, that is stressed to 232 lbs X
4g's(for an example). If you pull 232 lbs X 5 g's, then it will break.
That's why Va decreases with weight.

Toad
'3S'

toad wrote:
> The manufacturor would probably state the weight condition that Va
> applies for, ballasted or dry. I would expect that the Va was stated
> for dry.

The listing of all speeds at max gross weight is an aircraft industry
standard.

I just pulled out the POH for my LS6-b and page 2-2 lists 108 kts for
the rough air speed. There is no weight reference - your POH may vary.

Tony V. "6N"
http://home.comcast.net/~verhulst/SOARING

I have been watching this thread for a while now.

The term "rough air" seems somewhat subjective. Review of the various
aerodynamic manuals in my personal library does not give me a clue to what
gust load is used in rough air limit calculations or its' relationship to
the V-n diagram.

I am sure there is a precise definition which is used in to determine
performance limits. Could anyone provide the gust load definition of "rough
air?"

Respectfully,

Wayne
http://www.soaridaho.com/Schreder

You can be sure that it was calculated for dry, and then set as general
limit.
Aircraft industry standards are not necessarily applied when they don't make
sense...

"Tony Verhulst" > wrote in message
. ..
> toad wrote:
>> The manufacturor would probably state the weight condition that Va
>> applies for, ballasted or dry. I would expect that the Va was stated
>> for dry.
>
> The listing of all speeds at max gross weight is an aircraft industry
> standard.
>
> I just pulled out the POH for my LS6-b and page 2-2 lists 108 kts for the
> rough air speed. There is no weight reference - your POH may vary.
>
> Tony V. "6N"
> http://home.comcast.net/~verhulst/SOARING

On Sun, 12 Mar 2006 00:24:17 UTC, Bruce Hoult > wrote:

: Rough air places lower loads on a structure than do extreme control
: deflections

Surely that depends entirely on just how rough the air is?

Ian
--

In article <cCUlhtvFIYkV-pn2-g3gnB5bUeG9L@localhost>,
"Ian Johnston" > wrote:

> On Sun, 12 Mar 2006 00:24:17 UTC, Bruce Hoult > wrote:
>
> : Rough air places lower loads on a structure than do extreme control
> : deflections
>
> Surely that depends entirely on just how rough the air is?

True.

The point of rough air speed is that below that speed the structure will
be protected from breaking under the load from vertical gusts by the
wing stalling, which dramatically decreases the constant factor of the
aerodynamic forces.

There is still of course the V^2 factor, so the total force will rise
again to structural breaking point if the gusts are sufficiently strong
-- 100 m/s, say.

But at that point the speed you are flying at is irrelevant, so this
situation has no bearing on the setting of rough air speed.

--
Bruce | 41.1670S | \ spoken | -+-
Hoult | 174.8263E | /\ here. | ----------O----------

Wayne,

Thanks for the link.

Toad

Maneuvering speed and rough air speed are different
animals. For the curious, refer to JAR-22.341, which
begins with 'in the absence of a more rational analysis..'
and continues with an equation. The equation involves
a number of parameters, including the slope of the
wing lift curve and the wing chord - so it will vary
with sailplane model. There is no obvious relationship
between the rough air and maneuvering speeds, but JAR-22
also requires that the rough air speed must not be
less than the maneuvering speed. Of course, not all
sailplanes are subject to JAR-22.

http://www.tux.org/~milgram/temp/jar22.pdf

Ian

There is a common misconception of maneuvering speed among pilots that
somehow has been interpreted to be the maximum speed that will not
cause airframe damage with full and abrupt control deflections. THIS
IS WRONG! The November 2001 crash of the AA Airbus in New York was
determined to be from abrupt rudder deflections below maneuvering speed
resulting in the loss of the vertical fin.
http://www.flyingmag.com/article.asp?section_id=12&article_id=527
Maneuvering speed only relates to a limiting speed for wing protection
in a positive mode. Therefore, any full deflection of controls, other
than the elevator in a stick back mode, could result in failure of the
airframe. Also, since the wing is the only surface defined under
maneuvering speed, there could be a possible failure of elevator,
ailerons, fuselage, etc. with abrupt deflections.
http://www.x-plane.com/myths.html
In the USA, aircraft certification standards for maneuvering speed are
typically determined at gross weight in a clean configuration. As
mentioned in other posts, flying at weights below gross, or with flaps,
will cause a lower stall speed and a corresponding reduction in
maneuvering speed. The maximum positive g load subjected by the wing
before a stall will occur in any given configuration is calculated by
squaring the ratio of the aircraft speed divided by the unaccelerated
stall speed in the current configuration.

Bob Faris

W.J. (Bill) Dean (U.K.). wrote:
> I used to own an ASW20, Schleicher built early version with tip extensions.
>
> From memory the handbook explained what was meant by "rough air", it was
> described as a 15 m/s (30kt.) vertical gust. This might be running from
> still air into 30kt. up, or into 30kt. down, or from say 10kt. down into
> 20kt. up. The handbook also said that it was possible to find air rougher
> than that, for instance when running close to mountain ridges, in rotor, or
> in thunderstorms; and that if there was a risk of this lower speeds should
> be used.
>
> I think the possibility and danger of rougher air is obvious, after all what
> would happen if you tried soaring a big twister? I think that for a while
> you would go up very fast, but in bits.
>
> I have been looking at the book "Exploring the Monster". On 25th April
> 1955 Larry Edgar flying solo in the Pratt-Read was unable to keep out of the
> rotor, and the glider broke up, being subjected to at least 15G. He had
> entered the cloud at about 65 knots and had encountered a gust of about 85
> knots horizontal speed and a very large change in vertical speed. I
> suggest that no glider ever built could withstand this sort of thing, and if
> the glider could the pilot could not.
>
> As for manoeuvring speed, this is the limit speed for full deflection of any
> one control. Use another control as well and you are outside limits.
>
> W.J. (Bill) Dean (U.K.).
> Remove "ic" to reply.
>
> >
> > "Wayne Paul" > wrote in message
> > ...
> >
> > I have been watching this thread for a while now.
> >
> > The term "rough air" seems somewhat subjective. Review of the various
> > aerodynamic manuals in my personal library does not give me a clue to what
> > gust load is used in rough air limit calculations or its' relationship to
> > the V-n diagram.
> >
> > I am sure there is a precise definition which is used in to determine
> > performance limits. Could anyone provide the gust load definition of
> > "rough air?"
> >
> > Respectfully,
> >
> > Wayne
> > http://www.soaridaho.com/Schreder
> >

That does not apply to gliders under JAR22. At manoeuvering spped, you may
apply a full deflection of either aileron, rudder or elevator without
causing structural damage (but as Bill pointed out, not two of them).

"Bob Faris" > wrote in message
ups.com...
> Maneuvering speed only relates to a limiting speed for wing protection
> in a positive mode. Therefore, any full deflection of controls, other
> than the elevator in a stick back mode, could result in failure of the
> airframe. Also, since the wing is the only surface defined under
> maneuvering speed, there could be a possible failure of elevator,
> ailerons, fuselage, etc. with abrupt deflections.

Bert Willing wrote:
> You can be sure that it was calculated for dry, and then set as general
> limit.

How can I be sure?

Tony V

Common sense. Otherwise there would have to be a statement in the flight
manual that it depends on actual weight.

"Tony Verhulst" > wrote in message
. ..
> Bert Willing wrote:
>> You can be sure that it was calculated for dry, and then set as general
>> limit.
>
> How can I be sure?
>
> Tony V

At 01:06 14 March 2006, Bob Faris wrote:
>There is a common misconception of maneuvering speed
>among pilots
that
>somehow has been interpreted to be the maximum speed
>that will not
>cause airframe damage with full and abrupt control
>deflections. THIS
>IS WRONG! The November 2001 crash of the AA Airbus
>in New York
was
>determined to be from abrupt rudder deflections below
>maneuvering
speed
>resulting in the loss of the vertical fin.
>http://www.flyingmag.com/article.asp?section_id=12&article_id=527

I might be wrong here, but the AA Airbus break-up was
due to a repair
on the vertical fin spar. The Airbus flight controler
positions the controles
according to a program designed to limit the amount
of deflection so that
over stress does not occur. Everything runs through
the box.
Chuck

bagmaker wrote:
> Newbie help required!
> Lets suppose I am on a shallow final glide, 60k out in my 40:1 ship,
> cruising at 60 knots. Recent thermals have been at least 5 knots and I
> am coming into some big lift. For the discussion rough air Vne is 100
> knots.
> What strength thermal should I take to increase finishing speed to Vne
> and how much (if any) time will this save me?
> How do I estimate this at the time? What is the latest point on track
> to take such a thermal?

Once you HAVE final glide, you should not stop for lift unless you fall
below the glide path. If you have a 5kt thermal day, you will be on
final glide at a speed somewhat faster than 60kts!

As a rule of thumb, if you are in a gaggle climbing to achieve final
glide, the first one to leave will get home first (provided they have
enough height). I have tried staying in a 6 kt thermal and flying a 6kt
final glide rather than leaving at the 4kt final glide mark (when other
gliders left) and I did not catch them up, despite my higher speed.

On final glide, if I do hit lift, I may slow slightly to use the good
air but generally I hold my speed and keep flying. On a good day, you
can leave below final glide and pick up enough height to get home this way.