Oops, darn it...

[mvivion]

That accident and this one made me wonder if the elevator could have been used for pitch control. Elevators could perhaps operate as a stabilizer trim tab controlling pitch in reverse sense. I supppose it would depend on where the stab was hinged. So counter intuitive though that I doubt many pilots could push even if they knew the possibility of control reversal.

I'd bet the pilot didn't even have time to understand what was going on.....gives me the shivers.

MTV

 

[BC12D-4-85]

I think if I were a DHC-3 pilot I'd inquire about this prior incident liked in #3154. The details Docket in the original not linked form says never released:

20 June 1989 N41755 DHC-3 turbine involved in an incident.
The incident occurred at the Palmer Airport (PAQ) Palmer, AK, United States while on approach. The airplane pitched abruptly nose down following an inflight failure of the horizontal stabilizers trim actuator jack screw. The crew was able to maintain control of the airplane and make a successful landing by exerting a large amount of back pressure on the control wheel and adding nearly full engine power.

Edit: I assume upon trim actuator failure the forward hinged stabilizer assembly went rear down commanding a nose down attitude. The crew (two to three arms?) pulled back on the yokes (dual?) effecting up elevator to offset the dive. That and power blowing more air over the up elevator saved the day. One pilot with one arm available (maybe two if off power control) may not have the strength to accomplish that.

Gary

 

[BC12D-4-85]

One final thought re the DHC-3...I certainly hope a full elevator hand beats a trim at limits any day

Gary

 

[h2oavi8r]

Jack screw

AOPA has a good description and photo of the Jack screw. There’s also a diagram of the recovered parts of the accident DHC-3.

https://www.aopa.org/news-and-media...r-accident?utm_source=ebrief&utm_medium=email

 

[skywagon8a]

Heads Up Cessna flyers!

This accident report of a 185E on February 4,2021 in Chitina Alaska was brought to my attention by a friend.
http://www.kathrynsreport.com/2021/02/cessna-a185e-skywagon-n9725z-fatal.html

It appears the right lower lift strut fitting separated from the wing strut, apparently caused by the shearing of the countersunk rivets. This airplane only had 6569 hours total time, which doesn't seem to be high time for a working Alaska airplane of that vintage. Clearly it was used on skis which are known to generate a lot of punishment at times. Notice the pictures of the left wing strut ends where the paint is broken away around each rivet. That is a clear indication of motion between the rivets and the strut. It's likely that motion was sufficient for the movement of the right strut to shear the rivets. It looks like the lower rivets sheared first which created an uneven bending/shearing of the top rivets. It is also likely that the lower rivets had been moving or had been sheared for a period of time. How often does one look at the bottom rivets of the lower lift strut? Likely not often. One thing to bear in mind when using countersunk rivets in a highly shear loaded area, the strut material was countersunk which leaves a knife edge against the rivet. Then when the rivet starts to move, it acts like a guillotine shearing the rivets. Once one rivet shears the others have to take up the load with as in this case disastrous results.

I have noticed one or two smoking rivets on Cessna struts. On low time/years since new airplanes. Also have noticed that the countersinking in the struts as performed by Cessna was not very accurate. As in gaps around the rivet heads. Perhaps the countersinking of this strut was poorly done when it was manufactured? I've not heard of other Cessna struts separating, perhaps this was a fluke? Whatever, this is a good heads up for a more in depth strut rivet inspection.

What is a fix if this situation is discovered? Perhaps replacing the rivets with countersunk steel structural screws? Of course this would require an FAA blessing.

 

[BC12D-4-85]

It may not be related but those struts are used when accessing the fuel tanks by placing a weighted foot on them for support. Not sure of the stress on the strut's components if any caused by that procedure. Been lots of C-185's w/o strut failure, so maybe it's potentially a rare issue. Also, tying the plane down during high winds might create stress depending on method of securing (?). Examining the riveted area for wear would be good practice. What would be the best way to examine the strut fittings and rivets?

Gary

 

[stewartb]

180s have a plastic fairing that conceals that area. I don't think 185s have the same, so inspections would be easier. Tying down wouldn't stress the lower fitting much. The damage history to the right wing may play a role.

That was aktango's friend, right?

 

[BC12D-4-85]

I was thinking non-stretching tie downs like chains or cable (rare). Moving then an abrupt stop with shock to the strut. Most use ropes. Also the Docket notes a portion of the outboard top skin separated or departed the right wing at some point.

Docket: https://data.ntsb.gov/Docket?ProjectID=102605

Gary

 

[BC12D-4-85]

I briefly looked at two Cessnas parked nearby today...a C-180 and a C-185. The C-180 had no visible paint loss around the lower or upper outside strut rivets. The C-185 had one lower rivet on the right strut that showed some paint loss. Might happen over time? I flew two C-185's last Century but never looked. I did twist them on occasion to make sure they were still fastened top and bottom and they could move a little at the attachment fittings if provoked.

Gary

 

[hotrod180]

Heads Up Cessna flyers!
This accident report of a 185E on February 4,2021 in Chitina Alaska was brought to my attention by a friend.
http://www.kathrynsreport.com/2021/02/cessna-a185e-skywagon-n9725z-fatal.html
.....

Was a final report ever issued for this accident?
The passenger was a local guy from my area,
I know some of his relatives.

 

[BC12D-4-85]

Was a final report ever issued for this accident?
The passenger was a local guy from my area,
I know some of his relatives.

"The National Transportation Safety Board determines the probable cause(s) of this accident to be: An in-flight breakup during cruise flight for reasons that could not be determined based on available evidence. Findings: Not determined (general) - Unknown/Not determined"

Gary

 

[skywagon8a]

THAT ...

"The National Transportation Safety Board determines the probable cause(s) of this accident to be: An in-flight breakup during cruise flight for reasons that could not be determined based on available evidence. Findings: Not determined (general) - Unknown/Not determined"

Gary

... is a disappointment, since with just a cursory glance at some pictures there is ample evidence of a likely cause.

Sometimes it is wise to question the NTSB's accident analysis. For example: when the person who bought that airplane in my avitar did himself in with that airplane ....... the investigation was done from the office without ever visiting the site. I know this because I was there helping the State investigator, and the report didn't even have the correct make of engines installed.

 

[BC12D-4-85]

Review the Docket> https://data.ntsb.gov/Docket?ProjectID=102605 Note the prior damage and subsequent repairs. Some parts were replaced-repaired-reused. That may not be significant.

Gary

 

[stewartb]

The right wing had a big portion of the upper skin release and fold in half. The report doesn't indicate whether that happened before the strut failure or after, but in my feeble thinking it's more likely the wing skin caused the strut to fail than the other way around. As a Skywagon owner, I'm not sure what to take away from this report other than the root cause was likely related to the previous repairs to the right wing. I'm a bit surprised that the NTSB didn't dig deeper.

 

[wireweinie]

Legitimate question here: How would it be determined if the skin folded back before or after the strut broke? What evidence would be looked at?

Web

 

[skywagon8a]

The right wing had a big portion of the upper skin release and fold in half. The report doesn't indicate whether that happened before the strut failure or after, but in my feeble thinking it's more likely the wing skin caused the strut to fail than the other way around. As a Skywagon owner, I'm not sure what to take away from this report other than the root cause was likely related to the previous repairs to the right wing. I'm a bit surprised that the NTSB didn't dig deeper.

That is a good point. What did that other airplane hitting that wing do which transmitted damage to the lower end of the strut? It's possible the lower rivets partially sheared during that impact only to completely separate much later. That still doesn't take away from the fact the rest of the rivets do show evidence of being loose.

In that other report which Gary linked there is mention of the cabin roof being replaced. What was the cause of that repair? Were they related? The picture isn't clear enough to see any damage to the cabin top.

The strut also appears to have had electrical tape wrapped around it hiding any bad rivets. Why was the tape there? Certainly not for a place to place a foot?

Legitimate question here: How would it be determined if the skin folded back before or after the strut broke? What evidence would be looked at?

Web

It looks as though the lower rivets sheared allowing the fitting to bend upward while it pulled out of the strut, slicing the strut skin on either side of the fitting in the process.

 

[stewartb]

I’d expect them to inspect rivets and skin prep. For a skin to fold back enough to have aileron tracks imprinted would require it to be rigidly held against a tremendous amount of drag. And that wing was found in 5 pieces. It would have to have been attached to cause that. Once the skin folded the plane would have been uncontrollable. The wing coming apart after losing a skin might be expected. I’m not sure an intact wing coming off a plane would have done the same thing, but it might. I’m just trying to make sense of it.

 

[BC12D-4-85]

According to the Docket for N9725Z the donor of the right wing was a C-180 N91399 SN 18052069. It had experienced at least three prior "events"...06/09/79 St. Marys AK; 11/20/2005 Merrill Field AK; and 07/06/2014 Wasilla AK. What damage occurred or what parts were subsequently repaired I'll leave up to the reader to examine via an Internet search. That may have had no effect on this accident, however.

Gary

 

[skywagon8a]

So are you thinking the skin may have peeled back first, creating an overload which then failed the strut? I suppose that is possible, if the repairs were faulty. That skin peel damage is highly unlikely prior to some other failure as the structural loads on the skin in that area are very light. The wing damage appears more to me to be violent impact damage. My thoughts were based upon the evidence of loose rivets in the undamaged opposite strut having assumed both struts had loose and/or failed rivets. The failed rivet heads could have been captured by the electrical tape and thus unseen for a period of time. Just a time bomb waiting to go off!

 

[stewartb]

Yes, that's my thinking.

A section of right wing upper skin was separated that spanned from about WS 100 to WS 208.
The skin was folded in half lengthwise near the mid span point as recovered and straightened
during the exam. There were several V-shaped dents in the trailing edge gap seal between WS
156 and WS 185 consistent with the aileron skin stiffening corrugations. The outboard upper
skin panel was attached and had paint and markings consistent with being replaced. The upper
wing stringers remained attached to the skin and the WS 100 rib remained attached.

 

[Paul Heinrich]

Sitting, trapped in my truck after driving into a tree at 55 mph and being unable to extricate myself because of 11 broken ribs, a broken sternum, and a shattered pelvis, I realized just how helpless one can become even in “survivable” accidents. Had the truck caught fire or plunged into the nearby lake I would have died. No one would choose to go by water, fire, or falling from the sky depicted in too many of these Oops reports.

Condolences to the family and friends of those they lost.

 

[BC12D-4-85]

More would be learned if there were simple cockpit voice recorders available. I'm not suggesting mega thousand $ hard mounted devices, rather something that monitors and captures either intercom or transceiver voice for brief periods until overwritten. The overwrite interval need not be long. In these very sad events without some indication about what happened we are left having to analyze but mainly in the end assume. GPS' can store some basic recoverable flight data (typically as .CSV files). Why not offer something similar for general aviation cockpit audio?

Like this from here?

https://www.aircraftspruce.com/pages/ps/cockpitaccessories_recording/iphonecable11-12913.php

Gary

 

[stewartb]

New glass panels have “black box” function built in. A post-accident investigator can review the instruments right to the end.

 

[aktango58]

The failed rivet heads could have been captured by the electrical tape and thus unseen for a period of time. Just a time bomb waiting to go off!

The electrical tape was added to hold a cushion for when the door would get pushed into the strut to prevent damage to the door skin.

Lots of discussion on previous history of parts. My one thought is that history is minor in the scheme of things. What is important is what is the condition of the plane? History might suggest where to dig deeper in an inspection, but for pilots doing preflights- are we really going to dig through the entire history of a rental plane or friend's plane before we go flying? Or maybe we need to reset our pre-flight observations to no longer ignore smoking rivets?

Thank you Pete for bringing this discussion forward.

 

[StalledOut]

I have a little recorder, stores the last 15 seconds of whatever my headset hears. So a tower call, a transmission etc. Doesn't matter, it will store the last 15 seconds. Hit a button and it will replay it. Which comes in handy for my dad who uses the replay. I don't remember who builds it but I bought it at Oshkosh around 2010.

 

[BC12D-4-85]

I recall from the initial findings that the C-185 discussed here developed some brisk GPS ground speeds during the final descent. The NTSB examined the onboard GPS and noted it recorded a range of from 127 to finally 154 KTS GS while dropping about 1800' in ~5 minutes. Landes the wheel ski manufacturer earlier developed a couple of mandatory SB's that changed the bungee composition, rigging configuration, and established a Vno of 139 KTIAS - Vne 160 KTIAS. Just a comment that may have no bearing on this accident.

Gary

 

[skywagon8a]

Or maybe we need to reset our pre-flight observations to no longer ignore smoking rivets?

Smoking rivets in a wing skin are likely a minor issue, In a wing strut to fitting location ....... well that's another matter altogether. One must consider the location and what it does.

 

[Formandfunction]

Smoked rivets in a structural member is the failure of whomever signed that thing off as airworthy. Nobody is helping anybody signing stuff like that off. If the IA didn't know it was there he is equally responsible for not doing his job correctly.
If I had to guess it probably pulled the rivets out and as the wing rotated it ripped apart from the tip working it's way toward the fuselage. Totally avoidable accident

 

[skywagon8a]

A new proposed AD on the Otter trim system.
https://public-inspection.federalregister.gov/2022-23899.pdf

 

[S2D]

Smoked rivets in a structural member is the failure of whomever signed that thing off as airworthy. Nobody is helping anybody signing stuff like that off. If the IA didn't know it was there he is equally responsible for not doing his job correctly.

(a) Each person performing an annual or 100-hour inspection shall, before that inspection, remove or open all necessary inspection plates, access doors, fairing, and cowling. He shall thoroughly clean the aircraft and aircraft engine.

Keep in mind FAR 43 appendix D part (a)

Many times someone else cleans the airplane before the inspection. In this case it is easy to overlook a smoked rivet if not really loose.