LiFePo Refit Part 23 AC

[Shaun Wheeler]

SLA needs replacement and aircraft is part 23 utility. A LiFePo in the same foot print would be great, I definitely see folks using them and no less than three online stores selling them.

So I started looking at AC 20-184 which seems to be the FAA equivalent of trial by ordeal. Okay, I get it. They aren't quite as proven as SLA and a few have self immolated.

I've found at least a couple of EASA approvals that are sailplane specific but nothing that satisfies the lengthy list of hurdles the FSDO would likely accept.

Thoughts? Suggestions? Am I overthinking this?

[Eric Greenwell[_4_]]

Shaun Wheeler wrote on 2/26/2020 6:55 AM:
> SLA needs replacement and aircraft is part 23 utility. A LiFePo in the same foot print would be great, I definitely see folks using them and no less than three online stores selling them.
>
> So I started looking at AC 20-184 which seems to be the FAA equivalent of trial by ordeal. Okay, I get it. They aren't quite as proven as SLA and a few have self immolated.
>
> I've found at least a couple of EASA approvals that are sailplane specific but nothing that satisfies the lengthy list of hurdles the FSDO would likely accept.
>
> Thoughts? Suggestions? Am I overthinking this?

What is the aircraft that needs the battery? None of the gliders I've had
specified the chemistry of the instrument battery, and those were all easily
removable, suggesting they are "portable" units and not part of the aircraft.


--
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

[Shaun Wheeler]

L33 solo.

[2G]

On Wednesday, February 26, 2020 at 1:13:46 PM UTC-8, Shaun Wheeler wrote:
> L33 solo.

This may be of interest:
http://jdasolutions.aero/blog/faas-path-on-lithium-ion-battery-approval-standards/

https://www.aviationpros.com/engines-components/aircraft-airframe-accessories/batteries/article/12256058/lithiumion-batteries-in-aircraft

This is a TSO'd 12V battery:
https://earthxbatteries.com/product-category/certified-aircraft

To get approved it looks like any lithium ion battery will need a hardened case with venting to the outside of the A/C.

Tom

[Eric Greenwell[_4_]]

Shaun Wheeler wrote on 2/26/2020 1:13 PM:
> L33 solo.
>
Does the handbook specify the type of battery required for the instruments, or
prohibit LiFe batteries? If not, and it's easily removable, I think you can
reasonably claim it's a portable device and use one of your choosing in the
glider; after all, you likely have Lithium batteries in it already - your cell
phone, your inReach/Spot, your logger, and a handheld radio.

--
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]]

On Thursday, February 27, 2020 at 12:43:21 AM UTC-5, 2G wrote:
> On Wednesday, February 26, 2020 at 1:13:46 PM UTC-8, Shaun Wheeler wrote:
> > L33 solo.
>
> This may be of interest:
> http://jdasolutions.aero/blog/faas-path-on-lithium-ion-battery-approval-standards/
>
> https://www.aviationpros.com/engines-components/aircraft-airframe-accessories/batteries/article/12256058/lithiumion-batteries-in-aircraft
>
> This is a TSO'd 12V battery:
> https://earthxbatteries.com/product-category/certified-aircraft
>
> To get approved it looks like any lithium ion battery will need a hardened case with venting to the outside of the A/C.
>
> Tom

"at an incredible introductory price of $699"

This is for a starter type/size battery (it says "840 Peak cranking amp").

Curiously that web page does not say what the chemistry is, other than "lithium", but the PDF brochure says "Custom made prismatic LiFePo4 cells".

I wonder: the (large, installed) lithium batteries that caught fire on some airliners, what chemistry were they?

[Dave Walsh[_2_]]

At 17:17 27 February 2020, wrote:
>On Thursday, February 27, 2020 at 12:43:21 AM UTC-5, 2G
wrote:
>> On Wednesday, February 26, 2020 at 1:13:46 PM UTC-8,
Shaun Wheeler wrote:
>> > L33 solo.
>>
>> This may be of interest:
>>
>http://jdasolutions.aero/blog/faas-path-on-lithium-ion-battery-
approval-standards/
>>
>>
>https://www.aviationpros.com/engines-components/aircraft-
airframe-accessories/batteries/article/12256058/lithiumion-
batteries-in-aircraft
>>
>> This is a TSO'd 12V battery:
>> https://earthxbatteries.com/product-category/certified-aircraft
>>
>> To get approved it looks like any lithium ion battery will need a
>hardened case with venting to the outside of the A/C.
>>
>> Tom
>
>"at an incredible introductory price of $699"
>
>This is for a starter type/size battery (it says "840 Peak cranking
amp").
>
>Curiously that web page does not say what the chemistry is,
other than
>"lithium", but the PDF brochure says "Custom made prismatic
LiFePo4 cells".
>
>I wonder: the (large, installed) lithium batteries that caught fire
on some
>airliners, what chemistry were they?
>
The DreamLiner batteries were LiPo (Lithium Polymer) I think. I
understand they are now in an externally vented metal box? Any
Boeing pilots like to confirm?

[kinsell]

On 2/27/20 10:37 AM, Dave Walsh wrote:
> At 17:17 27 February 2020, wrote:
>> On Thursday, February 27, 2020 at 12:43:21 AM UTC-5, 2G
> wrote:
>>> On Wednesday, February 26, 2020 at 1:13:46 PM UTC-8,
> Shaun Wheeler wrote:
>>>> L33 solo.
>>>
>>> This may be of interest:
>>>
>> http://jdasolutions.aero/blog/faas-path-on-lithium-ion-battery-
> approval-standards/
>>>
>>>
>> https://www.aviationpros.com/engines-components/aircraft-
> airframe-accessories/batteries/article/12256058/lithiumion-
> batteries-in-aircraft
>>>
>>> This is a TSO'd 12V battery:
>>> https://earthxbatteries.com/product-category/certified-aircraft
>>>
>>> To get approved it looks like any lithium ion battery will need a
>> hardened case with venting to the outside of the A/C.
>>>
>>> Tom
>>
>> "at an incredible introductory price of $699"
>>
>> This is for a starter type/size battery (it says "840 Peak cranking
> amp").
>>
>> Curiously that web page does not say what the chemistry is,
> other than
>> "lithium", but the PDF brochure says "Custom made prismatic
> LiFePo4 cells".
>>
>> I wonder: the (large, installed) lithium batteries that caught fire
> on some
>> airliners, what chemistry were they?
>>
> The DreamLiner batteries were LiPo (Lithium Polymer) I think. I
> understand they are now in an externally vented metal box? Any
> Boeing pilots like to confirm?
>

Not a Boeing pilot, but they are lithium cobalt, like is used in most
electric motorgliders. Yes the 787 now uses steel boxes vented to the
outside.

But LiFePO4 have also been known to burn. EarthX says to vent them to
the outside, but don't believe they recommend fire-proof boxes.

Dave

[Shaun Wheeler]

The 'official' maintenance manual lists to model numbers, "NKDU 10" and "NKDU 10R" as optional equipment in the supplement index. This aircraft shipped with a Becker 3201 so it should also have shipped with the NKDU 10R battery, but the page for the battery "maintenance and operation" is missing. Neither battery appears to be in production anywhere these days. It's not listed on EASA either, I checked.

I did look through some of the reported fires before I asked about this. With a battery box, fuse and the correct hardware the risk for an aircraft that cannot recharge the cells in flight is almost non-existent.

[Shaun Wheeler]

Found a copy of the supplement page online.

The NKDU appears to have been NiCad cell strings with fillers that seal if rotated off 90 degrees. I'm not a chemist or a mechanical engineer (online or elsewhere) but that's my best translation of the electrolyte they want added.

I found where EASA and the FAA are trying to come up with something to solve this.

Most sailplanes aren't going to recharge in flight. That removes almost half the issues related to lithium cells on the front end. The electronics to balance cells are only relevant during the charging process. IMNSHO, they should waive those requirements on anything that does NOT require or provide for in-flight charging at any rate greater than what can be done with PV.

Anyways, thanks for the input. I think I've figured out what I'm going to do and thankfully, I'm not the only one doing it so if I'm wrong, well, I'm wrong in a lot of august company :)

[[email protected][_2_]]

Safety....you rationalize that.
FAA.......they’re watching us, the guinea pigs, before committing. So far, nobody's dying. The public safe. Press on.
Insurance....they don’t care unless it caused the accident. And now Lithiums are such an embedded part of our lives, I doubt they care.

I think you’re good to Soar.
R

[cdeerinck]

While not necessarily applicable to your situation, FYI, DG prohibits the use of any Lithium-Ion (even LiFePO4) in the tail compartment of its gliders, which surprised me, and foiled my plans. I suspect they have their reasons.

I don't know if that applies to an LS or not.

Best to check with them on what is allowed in your situation.

[John Foster]

On Friday, March 6, 2020 at 5:47:58 PM UTC-7, cdeerinck wrote:
> While not necessarily applicable to your situation, FYI, DG prohibits the use of any Lithium-Ion (even LiFePO4) in the tail compartment of its gliders, which surprised me, and foiled my plans. I suspect they have their reasons.
>
> I don't know if that applies to an LS or not.
>
> Best to check with them on what is allowed in your situation.

I wonder if that has as much to do with the weight (tail ballast) as much as it does with the fire hazard.

[Dan Marotta]

My LAK-17a had an SLA tail battery and it was needed as ballast. When I
got a LiFePO4 battery, I put it behind the seat and put a block of lead,
which matched the removed battery weight, in the tail.Â* I suppose I
could have simply left the dead battery there and saved some work but I
didn't want to risk it leaking.

On 3/6/2020 5:47 PM, cdeerinck wrote:
> While not necessarily applicable to your situation, FYI, DG prohibits the use of any Lithium-Ion (even LiFePO4) in the tail compartment of its gliders, which surprised me, and foiled my plans. I suspect they have their reasons.
>
> I don't know if that applies to an LS or not.
>
> Best to check with them on what is allowed in your situation.

--
Dan, 5J

[Dan Marotta]

Oh, and Fidel recommends removing the tail battery before trailering the
glider.Â* It should be apparent why.

On 3/7/2020 9:17 AM, Dan Marotta wrote:
> My LAK-17a had an SLA tail battery and it was needed as ballast. When
> I got a LiFePO4 battery, I put it behind the seat and put a block of
> lead, which matched the removed battery weight, in the tail.Â* I
> suppose I could have simply left the dead battery there and saved some
> work but I didn't want to risk it leaking.
>
> On 3/6/2020 5:47 PM, cdeerinck wrote:
>> While not necessarily applicable to your situation, FYI, DG prohibits
>> the use of any Lithium-Ion (even LiFePO4) in the tail compartment of
>> its gliders, which surprised me, and foiled my plans.Â* I suspect they
>> have their reasons.
>>
>> I don't know if that applies to an LS or not.
>>
>> Best to check with them on what is allowed in your situation.
>

--
Dan, 5J

[Eric Greenwell[_4_]]

From the LAK? Or all gliders? And just lithium batteries, or all types of
batteries? And what is the concern? I've never heard that advice before.

Dan Marotta wrote on 3/7/2020 8:19 AM:
> Oh, and Fidel recommends removing the tail battery before trailering the glider.
> It should be apparent why.
>
> On 3/7/2020 9:17 AM, Dan Marotta wrote:
>> My LAK-17a had an SLA tail battery and it was needed as ballast. When I got a
>> LiFePO4 battery, I put it behind the seat and put a block of lead, which matched
>> the removed battery weight, in the tail.* I suppose I could have simply left the
>> dead battery there and saved some work but I didn't want to risk it leaking.
>>
>> On 3/6/2020 5:47 PM, cdeerinck wrote:
>>> While not necessarily applicable to your situation, FYI, DG prohibits the use
>>> of any Lithium-Ion (even LiFePO4) in the tail compartment of its gliders, which
>>> surprised me, and foiled my plans.* I suspect they have their reasons.
>>>
>>> I don't know if that applies to an LS or not.
>>>
>>> Best to check with them on what is allowed in your situation.
>>
>


--
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

[Dan Marotta]

The recommendation is to remove weight which is placed high up in the
tail during road transport.Â* Jostling during trailering adds stress to
the aft fuselage at the base of the fin.Â* He has showed me very fine
cracks in the paint/gel coat.Â* Put simply:Â* Remove tail batteries before
trailering.

On 3/7/2020 10:13 AM, Eric Greenwell wrote:
> From the LAK? Or all gliders? And just lithium batteries, or all types
> of batteries? And what is the concern? I've never heard that advice
> before.
>
> Dan Marotta wrote on 3/7/2020 8:19 AM:
>> Oh, and Fidel recommends removing the tail battery before trailering
>> the glider.Â* It should be apparent why.
>>
>> On 3/7/2020 9:17 AM, Dan Marotta wrote:
>>> My LAK-17a had an SLA tail battery and it was needed as ballast.
>>> When I got a LiFePO4 battery, I put it behind the seat and put a
>>> block of lead, which matched the removed battery weight, in the
>>> tail.Â* I suppose I could have simply left the dead battery there and
>>> saved some work but I didn't want to risk it leaking.
>>>
>>> On 3/6/2020 5:47 PM, cdeerinck wrote:
>>>> While not necessarily applicable to your situation, FYI, DG
>>>> prohibits the use of any Lithium-Ion (even LiFePO4) in the tail
>>>> compartment of its gliders, which surprised me, and foiled my
>>>> plans.Â* I suspect they have their reasons.
>>>>
>>>> I don't know if that applies to an LS or not.
>>>>
>>>> Best to check with them on what is allowed in your situation.
>>>
>>
>
>

--
Dan, 5J

[[email protected]]

Seldom do glider owners care(read) what the regs say about equipment installed. I'm pleased you chased down the documents for your glider battery & looked at FAA guidance. And I'll join the preponderance of folks who get frustrated with regs not being "pertinent" or up-to-date with technology....

But to add a bit to the discussion, IF batteries are on the equipment list when it was weighed, they are not 'optional' payload. They then are considered part of the fixed installation, and glider should have weight placards for minimum solo and max pilot weights based on batteries IN for flight.

No one would argue that the chubby Gil or Concorde battery in the tow plane is 'optional', but it is removable.

For some club ships, with large members who need more payload, the weight & balance and equipment list might be better off with no batteries computed/listed.... and the lighter pilots can treat batteries as removable/installable payload.

I believe the DG restriction re: lithium of any style was due to an airframe fire.

And I have seen horrific wiring nightmares, and one case of a fuse in the panel allowing a bowed seatpan to short across terminals on the ground. The retired fireman pilot exited like a jackinthebox when I told him the glider was smoking.

Regardless of FAA guidance re: inflight accessibility of fuses, the origin protection fuse should be very close to a terminal on the battery.

I'll second the recommendation on batteries OUT for trailering. Especially tail fin installs.

Safe soaring,
Cindy B

[Eric Greenwell[_4_]]

wrote on 3/12/2020 1:35 AM:
> I'll second the recommendation on batteries OUT for trailering. Especially tail fin installs.

Is that based on gel coat cracking (the original reason for removing the tail
battery), the potential for fires caused by the battery while trailering, or to
protect the battery from damage during trailering?

Removing the main batteries from a Schleicher motorglider (ASH 26E and later), and
DG motorgliders is very time-consuming. Since I'm not aware of any problems caused
by leaving the main batteries in during trailering in these gliders, I think
removing and replacing them is likely to cause more problems than it avoids.

--
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

[Jonathon May]

If you are changing from, SLA to lipo the distance from the Cof G is
important .
Just changing the nose battery in a ventus to lipo could make for a very
interesting day.


At 14:43 12 March 2020, Eric Greenwell wrote:
wrote on 3/12/2020 1:35 AM:
>> I'll second the recommendation on batteries OUT for trailering.
>Especially tail fin installs.
>
>Is that based on gel coat cracking (the original reason for removing the
>tail
>battery), the potential for fires caused by the battery while trailering,
>or to
>protect the battery from damage during trailering?
>
>Removing the main batteries from a Schleicher motorglider (ASH 26E and
>later), and
>DG motorgliders is very time-consuming. Since I'm not aware of any
problems
>caused
>by leaving the main batteries in during trailering in these gliders, I
>think
>removing and replacing them is likely to cause more problems than it
>avoids.
>
>--
>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
>

[Dan Marotta]

Hi Eric,

The advice I got from Fidel was specific to batteries mounted high in
the vertical fin.Â* Think of an inverted pendulum.Â* The visible damage
appears as long cracks in the gel coat partially around the tail boom at
the leading edge of the base of the fin.Â* I wouldn't be surprised that
there would be damage to the underlying structure, but I have no direct
knowledge of that.Â* I doubt there's any mechanical problem with fuselage
mounted batteries, though I always removed mine so that they'd be fully
charged when I arrived at my destination.Â* They were ease to remove,
however.

Dan

On 3/12/2020 8:43 AM, Eric Greenwell wrote:
> wrote on 3/12/2020 1:35 AM:
>> I'll second the recommendation on batteries OUT for trailering.Â*
>> Especially tail fin installs.
>
> Is that based on gel coat cracking (the original reason for removing
> the tail battery), the potential for fires caused by the battery while
> trailering, or to protect the battery from damage during trailering?
>
> Removing the main batteries from a Schleicher motorglider (ASH 26E and
> later), and DG motorgliders is very time-consuming. Since I'm not
> aware of any problems caused by leaving the main batteries in during
> trailering in these gliders, I think removing and replacing them is
> likely to cause more problems than it avoids.
>

--
Dan, 5J

[Dan Marotta]

That's why when I replaced the SLA tail battery in my Experimental
LAK-17a with a LiFePO4, I placed the new battery behind the seat back.Â*
I replaced the weight removed from the tail with an ingot of lead of the
same weight as the battery that was removed.Â* The lead ingot was sealed
in the LAK removable battery box that was designed to fit that location.

On 3/12/2020 9:10 AM, Jonathon May wrote:
> If you are changing from, SLA to lipo the distance from the Cof G is
> important .
> Just changing the nose battery in a ventus to lipo could make for a very
> interesting day.
>
>
> At 14:43 12 March 2020, Eric Greenwell wrote:
>> wrote on 3/12/2020 1:35 AM:
>>> I'll second the recommendation on batteries OUT for trailering.
>> Especially tail fin installs.
>>
>> Is that based on gel coat cracking (the original reason for removing the
>> tail
>> battery), the potential for fires caused by the battery while trailering,
>> or to
>> protect the battery from damage during trailering?
>>
>> Removing the main batteries from a Schleicher motorglider (ASH 26E and
>> later), and
>> DG motorgliders is very time-consuming. Since I'm not aware of any
> problems
>> caused
>> by leaving the main batteries in during trailering in these gliders, I
>> think
>> removing and replacing them is likely to cause more problems than it
>> avoids.
>>
>> --
>> 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
>>
>

--
Dan, 5J

[Eric Greenwell[_4_]]

The horizontal stabilizer on a glider weighs far more than any of the tail
batteries I've encountered, and when flying the glider, especially the takeoff and
landing, that heavy horizontal puts a lot more forces (vertically and twisting) on
the tail boom than the battery. In a trailer, the forces are almost entirely
vertical, and are also far less than the landing/takeoff pounding the tail gets.
So I'm skeptical the gel coat cracking is due to the battery during trailering.

How did Fidel determine it was the battery/trailering, and not the normal
operation of the glider, or some other cause?


Dan Marotta wrote on 3/12/2020 10:06 AM:
> Hi Eric,
>
> The advice I got from Fidel was specific to batteries mounted high in the vertical
> fin.* Think of an inverted pendulum.* The visible damage appears as long cracks in
> the gel coat partially around the tail boom at the leading edge of the base of the
> fin.* I wouldn't be surprised that there would be damage to the underlying
> structure, but I have no direct knowledge of that.* I doubt there's any mechanical
> problem with fuselage mounted batteries, though I always removed mine so that
> they'd be fully charged when I arrived at my destination.* They were ease to
> remove, however.
>
> Dan
>
> On 3/12/2020 8:43 AM, Eric Greenwell wrote:
>> wrote on 3/12/2020 1:35 AM:
>>> I'll second the recommendation on batteries OUT for trailering. Especially tail
>>> fin installs.
>>
>> Is that based on gel coat cracking (the original reason for removing the tail
>> battery), the potential for fires caused by the battery while trailering, or to
>> protect the battery from damage during trailering?
>>
>> Removing the main batteries from a Schleicher motorglider (ASH 26E and later),
>> and DG motorgliders is very time-consuming. Since I'm not aware of any problems
>> caused by leaving the main batteries in during trailering in these gliders, I
>> think removing and replacing them is likely to cause more problems than it avoids.
>>
>


--
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

[Dan Marotta]

It's just a simple thing you can do to remove one risk factor.Â* Take it
for what it's worth and do what you like.

On 3/12/2020 12:09 PM, Eric Greenwell wrote:
> The horizontal stabilizer on a glider weighs far more than any of the
> tail batteries I've encountered, and when flying the glider,
> especially the takeoff and landing, that heavy horizontal puts a lot
> more forces (vertically and twisting) on the tail boom than the
> battery. In a trailer, the forces are almost entirely vertical, and
> are also far less than the landing/takeoff pounding the tail gets. So
> I'm skeptical the gel coat cracking is due to the battery during
> trailering.
>
> How did Fidel determine it was the battery/trailering, and not the
> normal operation of the glider, or some other cause?
>
>
> Dan Marotta wrote on 3/12/2020 10:06 AM:
>> Hi Eric,
>>
>> The advice I got from Fidel was specific to batteries mounted high in
>> the vertical fin.Â* Think of an inverted pendulum.Â* The visible damage
>> appears as long cracks in the gel coat partially around the tail boom
>> at the leading edge of the base of the fin.Â* I wouldn't be surprised
>> that there would be damage to the underlying structure, but I have no
>> direct knowledge of that.Â* I doubt there's any mechanical problem
>> with fuselage mounted batteries, though I always removed mine so that
>> they'd be fully charged when I arrived at my destination.Â* They were
>> ease to remove, however.
>>
>> Dan
>>
>> On 3/12/2020 8:43 AM, Eric Greenwell wrote:
>>> wrote on 3/12/2020 1:35 AM:
>>>> I'll second the recommendation on batteries OUT for trailering.
>>>> Especially tail fin installs.
>>>
>>> Is that based on gel coat cracking (the original reason for removing
>>> the tail battery), the potential for fires caused by the battery
>>> while trailering, or to protect the battery from damage during
>>> trailering?
>>>
>>> Removing the main batteries from a Schleicher motorglider (ASH 26E
>>> and later), and DG motorgliders is very time-consuming. Since I'm
>>> not aware of any problems caused by leaving the main batteries in
>>> during trailering in these gliders, I think removing and replacing
>>> them is likely to cause more problems than it avoids.
>>>
>>
>
>

--
Dan, 5J

[[email protected]]

The loads and vibration imparted while trailering far exceed flight loads. Bob Carlton has trailered his airshow Salto around the country for years, and I can attest that a simple ten mile trip on the road will peg the G-Meter at +10 and -10 Gs. Side loads are probably not as severe, but we have no method of measuring those loads, simply because the Salto has a "V" tail, and the tail airfoils are removed for transport.

One thing I installed in my 1983 Cobra trailer is a thick foam pad at the top of the rudder box. When the trailer top is pulled down into the closed position, the foam compresses against the top of the rudder, damping side-to-side motion and vibration.

Still, it's a good idea to remove the top mounted tail battery. Gelcoat repairs aren't cheap, but fiberglass work is really expensive. Ask me how I know this.

[Eric Greenwell[_4_]]

wrote on 3/12/2020 6:26 PM:
> The loads and vibration imparted while trailering far exceed flight loads. Bob Carlton has trailered his airshow Salto around the country for years, and I can attest that a simple ten mile trip on the road will peg the G-Meter at +10 and -10 Gs. Side loads are probably not as severe, but we have no method of measuring those loads, simply because the Salto has a "V" tail, and the tail airfoils are removed for transport.
>
> One thing I installed in my 1983 Cobra trailer is a thick foam pad at the top of the rudder box. When the trailer top is pulled down into the closed position, the foam compresses against the top of the rudder, damping side-to-side motion and vibration.
>
> Still, it's a good idea to remove the top mounted tail battery. Gelcoat repairs aren't cheap, but fiberglass work is really expensive. Ask me how I know this.

Typical mechanical G meters used in airplanes are very poor accelerometers. They
are underdamped, and respond to jostling by overshooting and oscillating. They do
a fine job measuring the much lower frequencies encountered during aerobatic
flight, but not the rattle and shake vehicle produces rolling down the road. Take
off from a bumpy grass strip, and you'll see the instrument peg itself.

In fact, measuring structural loads can be very complex. You can be certain that
10 g loads are not being transmitted from the tail battery to the tail boom, for
at least two reasons: the battery is not being subjected to 10 g loads, and the
frequencies of the loads that do exist are high enough that the loads are being
damped harmlessly by the intervening structure.

There is a good reason that none of the manufacturers require the tail battery to
be removed during trailering: it does no harm. Anyone concerned about the safety
of leaving the battery in the tail should contact their glider's manufacturer for
the correct procedures.

--
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

[Dan Marotta]

Mark, if you're really interested you could rotate the G-meter 90
degrees in either direction. :-D

On 3/12/2020 7:26 PM, wrote:
> The loads and vibration imparted while trailering far exceed flight loads. Bob Carlton has trailered his airshow Salto around the country for years, and I can attest that a simple ten mile trip on the road will peg the G-Meter at +10 and -10 Gs. Side loads are probably not as severe, but we have no method of measuring those loads, simply because the Salto has a "V" tail, and the tail airfoils are removed for transport.
>
> One thing I installed in my 1983 Cobra trailer is a thick foam pad at the top of the rudder box. When the trailer top is pulled down into the closed position, the foam compresses against the top of the rudder, damping side-to-side motion and vibration.
>
> Still, it's a good idea to remove the top mounted tail battery. Gelcoat repairs aren't cheap, but fiberglass work is really expensive. Ask me how I know this.

--
Dan, 5J