Service Ceiling L23 - Litigation

[[email protected]]

After reading the article I retrieved my copy of the L23 flight manual. Where does it say you can't fly it higher than 12,805 feet? There are VNE reductions calculated up to 35,000, but nowhere in it can I find a service ceiling limitation as the plaintiff seems to suggest there are.

Did I miss something?

Note:I am aware of the differences between flight test for certification and the extrapolation used to prepare the manual.


https://trib.com/news/state-and-regional/teton-aviation-sued-after-fatal-plane-crash-in-2018/article_5d2c5904-426f-531c-af91-675249be5d1c.html

[Haven]

I didn't see any discussion of service ceiling. Back ~'98 I had a great ride in a two-place Grob 103 at Driggs, where we made a couple of circuits around the Grand Teton waving at the mountain climbers. Can't remember how high we were upon release or much more detail of the flight. The G103 and L23 have similar performance figures but it is all dependent on the skill and judgment of the pilot. Absent evidence of structural or flight controls/surfaces failure we are left with pilot error as the cause of the accident.

On Wednesday, December 16, 2020 at 7:06:26 PM UTC-8, wrote:
> After reading the article I retrieved my copy of the L23 flight manual. Where does it say you can't fly it higher than 12,805 feet? There are VNE reductions calculated up to 35,000, but nowhere in it can I find a service ceiling limitation as the plaintiff seems to suggest there are.
>
> Did I miss something?
>
> Note:I am aware of the differences between flight test for certification and the extrapolation used to prepare the manual.
>
>
> https://trib.com/news/state-and-regional/teton-aviation-sued-after-fatal-plane-crash-in-2018/article_5d2c5904-426f-531c-af91-675249be5d1c.html

[[email protected]]

On Thursday, December 17, 2020 at 1:11:08 AM UTC-5, Haven wrote:
> I didn't see any discussion of service ceiling. Back ~'98 I had a great ride in a two-place Grob 103 at Driggs, where we made a couple of circuits around the Grand Teton waving at the mountain climbers. Can't remember how high we were upon release or much more detail of the flight. The G103 and L23 have similar performance figures but it is all dependent on the skill and judgment of the pilot. Absent evidence of structural or flight controls/surfaces failure we are left with pilot error as the cause of the accident.
> On Wednesday, December 16, 2020 at 7:06:26 PM UTC-8, wrote:
> > After reading the article I retrieved my copy of the L23 flight manual. Where does it say you can't fly it higher than 12,805 feet? There are VNE reductions calculated up to 35,000, but nowhere in it can I find a service ceiling limitation as the plaintiff seems to suggest there are.
> >
> > Did I miss something?
> >
> > Note:I am aware of the differences between flight test for certification and the extrapolation used to prepare the manual.
> >
> >
> > https://trib.com/news/state-and-regional/teton-aviation-sued-after-fatal-plane-crash-in-2018/article_5d2c5904-426f-531c-af91-675249be5d1c.html


Maybe they didn't have oxygen on that flight?
RO

[Frank Whiteley]

On Wednesday, December 16, 2020 at 8:06:26 PM UTC-7, shaun_xxxxxxxxxxx wrote:
> After reading the article I retrieved my copy of the L23 flight manual. Where does it say you can't fly it higher than 12,805 feet? There are VNE reductions calculated up to 35,000, but nowhere in it can I find a service ceiling limitation as the plaintiff seems to suggest there are.
>
> Did I miss something?
>
> Note:I am aware of the differences between flight test for certification and the extrapolation used to prepare the manual.
>
>
> https://trib.com/news/state-and-regional/teton-aviation-sued-after-fatal-plane-crash-in-2018/article_5d2c5904-426f-531c-af91-675249be5d1c.html
Shawn there are a number of L-23 Pilot Manuals PDF'd on the web. There are page revisions to most, but the PDFs may be dated. Ours was N392BA and appears on a few sites. It was sold and exported to Argentina several years ago. That page has the limit in one or more version, yet it's missing from others. So there may have been page changes made to the Pilot Manual and applied inconsistently.
The manual lists the 'demonstrated' ceiling in para 2.11, but it's manual page revision number is 1012.3 and is listed as S/N 978307, no N-number. It appears to apply to serial numbers 938101 and subsequent.
http://www.cagcsoaring.ca/wp-content/uploads/2016/04/L-23-Super-Blanik.pdf
It's in this copy
http://www.soarccsc.com/wp-content/uploads/2015/09/L-23-Super-Blanik-Flight-Manual.pdf

It does not appear in manual version/revision 1014.5 for serial numbers 029005 and subsequent.

So, it's a tough question. There were some payload changes from some of the earlier serial number. The first two digits are year of manufacture. Were there pilot manual page inserts that updated the pilot manual? I don't think demonstrated service altitude is a service limit.

FAA TCDS info for G60EU_Rev8
https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/4be37cc5c028c09f86258115005f3e32/$FILE/G60EU_Rev_8.pdf

No pilot manual mentions an altitude placard. I certainly soared ours up to 17,500 several times.

The accident docket is here https://data.ntsb.gov/Docket?ProjectID=97436

Frank Whiteley

[2G]

On Thursday, December 17, 2020 at 3:12:22 PM UTC-8, Frank Whiteley wrote:
> On Wednesday, December 16, 2020 at 8:06:26 PM UTC-7, shaun_xxxxxxxxxxx wrote:
> > After reading the article I retrieved my copy of the L23 flight manual. Where does it say you can't fly it higher than 12,805 feet? There are VNE reductions calculated up to 35,000, but nowhere in it can I find a service ceiling limitation as the plaintiff seems to suggest there are.
> >
> > Did I miss something?
> >
> > Note:I am aware of the differences between flight test for certification and the extrapolation used to prepare the manual.
> >
> >
> > https://trib.com/news/state-and-regional/teton-aviation-sued-after-fatal-plane-crash-in-2018/article_5d2c5904-426f-531c-af91-675249be5d1c.html
> Shawn there are a number of L-23 Pilot Manuals PDF'd on the web. There are page revisions to most, but the PDFs may be dated. Ours was N392BA and appears on a few sites. It was sold and exported to Argentina several years ago. That page has the limit in one or more version, yet it's missing from others. So there may have been page changes made to the Pilot Manual and applied inconsistently.
> The manual lists the 'demonstrated' ceiling in para 2.11, but it's manual page revision number is 1012.3 and is listed as S/N 978307, no N-number. It appears to apply to serial numbers 938101 and subsequent.
> http://www.cagcsoaring.ca/wp-content/uploads/2016/04/L-23-Super-Blanik.pdf
> It's in this copy
> http://www.soarccsc.com/wp-content/uploads/2015/09/L-23-Super-Blanik-Flight-Manual.pdf
>
> It does not appear in manual version/revision 1014.5 for serial numbers 029005 and subsequent.
>
> So, it's a tough question. There were some payload changes from some of the earlier serial number. The first two digits are year of manufacture. Were there pilot manual page inserts that updated the pilot manual? I don't think demonstrated service altitude is a service limit.
>
> FAA TCDS info for G60EU_Rev8
> https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/4be37cc5c028c09f86258115005f3e32/$FILE/G60EU_Rev_8.pdf
>
> No pilot manual mentions an altitude placard. I certainly soared ours up to 17,500 several times.
>
> The accident docket is here https://data.ntsb.gov/Docket?ProjectID=97436
>
> Frank Whiteley

The point in the complaint “being towed and released at an altitude that exceeded the certification and rating of the glider” is specious and not supported in the POH. The accident docket, however, contains several disturbing examples of poor pilotage. The pilot was flying very uncoordinated at low airspeeds close to the terrain. Additionally, there were indications of strong gusting winds at the time of the accident and the glider encountered strong sink multiple times shortly before the accident. Twice the pilot said "this is not good" prior to the accident as recorded by the passenger's smartphone, indicating she did not have situational awareness. The accident photo showed a vertical impact, so the pilot likely entered a stall/spin. This accident was totally preventable by maintaining some extra airspeed and flying coordinated. It is interesting that the docket includes a Soaring article on mountain flying by Henry Combs in 1984, which gives me a strong indication of where the investigation is heading.

Tom

[[email protected]]

Thank you for the responses.

I could not find anything to support counsel's mendacious claim that the aicraft was towed or flown above any restriction either by the manufacturer or by the FAA. The evidence seems to support your opinion, Tom, that she got into sink and did not correct accordingly. Why was she so far out of trim? 45 degrees in the front seat isn't something you wouldn't notice from the back.

[Stuart Venters]

On 12/17/20 10:03 PM, wrote:
> Thank you for the responses.
>
> I could not find anything to support counsel's mendacious claim that the aicraft was towed or flown above any restriction either by the manufacturer or by the FAA. The evidence seems to support your opinion, Tom, that she got into sink and did not correct accordingly. Why was she so far out of trim? 45 degrees in the front seat isn't something you wouldn't notice from the back.
>
>
>
There is a mention of 12-5 in the accident report interviews.

https://data.ntsb.gov/Docket/Document/docBLOB?ID=40485387&FileExtension=.PDF&FileName=TAC%20Company%20Interviews%20-Master.PDF

Page 104 line 3 regarding the length or glider flights.

3 A. It would be to be 2 hours. But that being said, even if it
4 is, we're never above 12-5 for more than 30 minutes due to the
5 oxygen requirements. So we have that kind of ceiling.

[2G]

On Thursday, December 17, 2020 at 8:03:51 PM UTC-8, wrote:
> Thank you for the responses.
>
> I could not find anything to support counsel's mendacious claim that the aicraft was towed or flown above any restriction either by the manufacturer or by the FAA. The evidence seems to support your opinion, Tom, that she got into sink and did not correct accordingly. Why was she so far out of trim? 45 degrees in the front seat isn't something you wouldn't notice from the back.

By "trim" I assume that you mean rudder coordination and not nose-down trim.. I assume that there is a yaw string for the back seat as the front yaw string would not be visible to the pilot. She was both allowing airspeed to bleed off to dangerously slow levels and not monitoring control coordination.. It is puzzling why, after twice saying "This is not good" that she didn't turn back to the airport.

The lawyer is probably not a pilot and may have interpreted the O2 altitude limitation to be an airframe limitation. He has plenty of malfeasances to hold Teton Aviation's feet to the fire, however.

Tom

[Tango Eight]

On Saturday, December 19, 2020 at 5:09:01 PM UTC-5, 2G wrote:
> On Thursday, December 17, 2020 at 8:03:51 PM UTC-8, wrote:
> > Thank you for the responses.
> >
> > I could not find anything to support counsel's mendacious claim that the aicraft was towed or flown above any restriction either by the manufacturer or by the FAA. The evidence seems to support your opinion, Tom, that she got into sink and did not correct accordingly. Why was she so far out of trim? 45 degrees in the front seat isn't something you wouldn't notice from the back.
> By "trim" I assume that you mean rudder coordination and not nose-down trim. I assume that there is a yaw string for the back seat as the front yaw string would not be visible to the pilot. She was both allowing airspeed to bleed off to dangerously slow levels and not monitoring control coordination. It is puzzling why, after twice saying "This is not good" that she didn't turn back to the airport.
>
> The lawyer is probably not a pilot and may have interpreted the O2 altitude limitation to be an airframe limitation. He has plenty of malfeasances to hold Teton Aviation's feet to the fire, however.
>
> Tom


Look through the photos in item 30 on the docket linked earlier in the thread (still frames from video the passenger was recording in the moments before the crash), it's very strange. Ridge on the left, very close aboard (less than 100 feet is my guess), left bank about 30 degrees, yaw string indicating what appears to be full right rudder. The full video would probably provide additional insight. The last two frames, 9 seconds apart, don't show evidence of a rapid descent... comparing the two views with the ridge line and considering the severe uncoordinated flight condition, I would guess the glider is flying in lift.

More questions than answers.

T8

[[email protected]]

Grand Teton is 13,776 ft. Icefloe Lake is 10,652 ft. If the first frame began at release altitude then they were slightly below and to the south of the summit of Grand Teton. In 3:09 they lost 3100 feet give or take.


https://www.youtube.com/watch?v=lvWNkP-NzAQ

[Tango Eight]

On Sunday, December 20, 2020 at 1:43:57 AM UTC-5, wrote:
> Grand Teton is 13,776 ft. Icefloe Lake is 10,652 ft. If the first frame began at release altitude then they were slightly below and to the south of the summit of Grand Teton. In 3:09 they lost 3100 feet give or take.
>
>
> https://www.youtube.com/watch?v=lvWNkP-NzAQ

The saddle of the ridgeline level with the glider Figure 7, time stamp 3:06, is 11,500. It doesn't look like there was any altitude loss to speak of, and perhaps a small gain between 2:57 and 3:06.

If a spin event happened shortly after 3:06, it may not have happened like in the linked video. When stalled in a full rudder over slipping turn of 30 degrees bank, the L-23 spins into the low wing, -against- the rudder. The entry looks similar to Figure 7 (but desirably without rocks). In that case, expect an excursion to 60 degrees nose low pitch, about 180 degrees of (slow) auto rotation before recovery and a few hundred feet of altitude lost. I have done many times with students as a part of a lesson on slips and slipping turns.

T8

[jp]

On Sunday, December 20, 2020 at 5:56:29 AM UTC-8, wrote:
> On Sunday, December 20, 2020 at 1:43:57 AM UTC-5, wrote:
> > Grand Teton is 13,776 ft. Icefloe Lake is 10,652 ft. If the first frame began at release altitude then they were slightly below and to the south of the summit of Grand Teton. In 3:09 they lost 3100 feet give or take.
> >
> >
> > https://www.youtube.com/watch?v=lvWNkP-NzAQ
> The saddle of the ridgeline level with the glider Figure 7, time stamp 3:06, is 11,500. It doesn't look like there was any altitude loss to speak of, and perhaps a small gain between 2:57 and 3:06.
>
> If a spin event happened shortly after 3:06, it may not have happened like in the linked video. When stalled in a full rudder over slipping turn of 30 degrees bank, the L-23 spins into the low wing, -against- the rudder. The entry looks similar to Figure 7 (but desirably without rocks). In that case, expect an excursion to 60 degrees nose low pitch, about 180 degrees of (slow) auto rotation before recovery and a few hundred feet of altitude lost. I have done many times with students as a part of a lesson on slips and slipping turns.
>
> T8

That is very helpful information Tango. I'll have to try that. I've thought that in an uncoordinated stall the aircraft will roll "to the rudder", not against the rudder. So, in the example you describe I would have thought that the "outside" wing, in this case the high wing, would be in the wind shadow of the fuselage and so would stall first thereby having the aircraft roll to that wing - sometimes called "over the top". On the other hand I have not flown an L-23. Also, maybe the 30 degree bank makes a difference.. I have been wrong in a very important circumstance.

[2G]

On Sunday, December 20, 2020 at 5:56:29 AM UTC-8, wrote:
> On Sunday, December 20, 2020 at 1:43:57 AM UTC-5, wrote:
> > Grand Teton is 13,776 ft. Icefloe Lake is 10,652 ft. If the first frame began at release altitude then they were slightly below and to the south of the summit of Grand Teton. In 3:09 they lost 3100 feet give or take.
> >
> >
> > https://www.youtube.com/watch?v=lvWNkP-NzAQ
> The saddle of the ridgeline level with the glider Figure 7, time stamp 3:06, is 11,500. It doesn't look like there was any altitude loss to speak of, and perhaps a small gain between 2:57 and 3:06.
>
> If a spin event happened shortly after 3:06, it may not have happened like in the linked video. When stalled in a full rudder over slipping turn of 30 degrees bank, the L-23 spins into the low wing, -against- the rudder. The entry looks similar to Figure 7 (but desirably without rocks). In that case, expect an excursion to 60 degrees nose low pitch, about 180 degrees of (slow) auto rotation before recovery and a few hundred feet of altitude lost. I have done many times with students as a part of a lesson on slips and slipping turns.
>
> T8

If you look at the photos of the accident site it is apparent that there was not that much altitude loss between spin entry and impact, perhaps 500 - 1000 feet. Yes, the full video would be very helpful in analyzing the sequence of events. Certainly, the lawyers have access to it, which no doubt will be presented at trial (assuming it goes to trial).

Tom