The FAA issued an airworthiness concern sheet (ACS) after a cockpit power lever fractured on a Cirrus SR20 as the pilot advanced the throttle for takeoff. The pilot cut fuel to the engine and safely aborted the takeoff. Follow-up visual and dye-penetrant examinations by the training fleet operator revealed cracks in 24 more aircraft. The original failure and the cracks discovered in the remaining aircraft all were located near the section of the power levers with the smallest cross section. The ACS covers all SR-series Cirrus models, including the SR20, SR22 and SR22T.
Judging from the number of landings these are flight school planes with a lot of students learning to not jam the throttle. Still it does seem like a weak point looking at the fracture point. One thing I keep wondering is why are small plane manufacturers not ever required to announce a recall like auto manufacturers and fix their design flaws? It seems it always falls to the owner to correct.
How about a little context? What goes into that cutout in the throttle lever? A bolt? A cable bead? And why only a ACS? Even if that operator had 100 planes, that’s still a 25% failure rate at a known time. This defect requires a new design, clearly. If that break happened after takeoff, a low time pilot would have a tough time managing energy, altitude, and flap speeds to accomplish a landing. Is the FAA following a required procedure here? Is this an overcautious officer? What more statistical info is required? A replacement looks like an easy install. And Only 20 samples are needed for a 95% confidence level. They have 24.
The ACS process was lobbied by industry stakeholders and implemented by the FAA in response to concerns that regulatory decisions were/may be made without having all information available prior to making a decision.
My eyeball engineering look at it does seem to say not a very stout looking lever considering it gets pushed and pulled constantly. I went to the OKC GADO years ago to take a CFI flight test. The guy was just plane mean and rude. I was an airman up at Vance AFB. We finally decided to go do the flying portion. As he got into the C150, his leg bumped the throttle and bent it about ninety degrees up. He just said,“if you can get that fixed, let me know.” then he got out slammed the door and walked away. I walked over to a nearby FBO and told a mechanic my needs. He came over and with his hand bent it back straight, no charge or paperwork. I retrieved the FADO guy and away we went. Wind was gusting to about 30. On takeoff the stall horn beeped once with a gust. He said, “son, you just about killed us”. I was thinking I was wasting my time. He did actually pass me. I think it was maybe remorse about bending the throttle. 1967 and I still remember his name.
Vibration and ham fisting will eventually lead to crack initiaition in aluminum alloys. It is had to determine initiation site as the pictures do not show enough detail. However with the fleet examination showing the number of issues I would call Cirrus after the FAA reporting and have a chat about replacement parts vis a vis how many AC have been purchased. One of those quite friendly chats that have the background (unstated) of what kind of S*(t may be coming next).
Humans typically react to the ergonomics presented, so a nice robust handle needs to be connected to an equally robust shaft, regardless of the actual actuating force required to do the job.
I do not understand why they discuss ALL SR series. I am certain that neither G1 nor G2 use this style handle. Mine is a flat stamped solid metal bar. This one looks like a hollow square tube.
I think they want to be sure that the problem is confined to the ones that have the hollow center for the wire. The same area is probably pretty stressed on the solid ones and they want to be sure.
Thanks. So it’s the Takeoff/Go Around button. I gather then, that the opening is a wire exit point and the wire routes upward INSIDE that lever? Note the rounded corners to avoid wear on the wire insulation perhaps. Admitedly I’m speculating because I have not looked at this part of a Cirrus.