Challenger 300 Turbulence Death - Prelim Released

[GypsyPilot]

I could totally see how this could happen to even good pilots who couldn’t separate the perceived pressures from Mr Big and doing a good enough job to not kill someone.

Last minute call outs to the airport, someone telling you “oh the airplane is good to go” when you show up. Then being afraid to stop the operation and admit to Mr Big: “hey this went bad we need fo shut the airplane down and hard reset to make it work.”

Now you kill Mr. Bigs wife trying to make him happy and you could go to jail for it.

Absolutely no excuse for any of that stuff these days, particularly for people as experienced as this crew was.

Yes I did some really stupid stuff when I was a low time commercial pilot just lucky to have a job in the dark days of the mid 2000s. But no excuse for that these days, particularly as experienced pilots.

I’m certainly not immune from making mistakes, and I do make them. But I also admit it immediately and try to do the right thing. It seems like there was a lot of attempted CYA here, and that’s inexcusable. It’s also one of the only ways you could get fired at the regional you and I worked at, as well as my current employer.

 

[KLB]

That’s a good point, I assume config and Mach trim also use the secondary trim motor?

Likely. Because secondary trim moves at a much slower rate than primary trim.

Here's the procedure for an autopilot stab trim fail. The trim system automatically cuts out of it trims continuously. You'd get this message with the autopilot on and have to do this procedure.

 

[Roger Roger]

So along with your Prime Stab and secondary stab trim, there is also configuration trim and mach trim which are done without pilot input. They are based on speed and configuration. I am not sure if a clogged pitot tube giving an erroneous reading could effect how mach trim works in cruise....if that makes sense.

I’m also curious about the multiple autopilot disconnects they had prior in the climb. Im certainly not mr super pilot but i and everyone else I fly with leaves Otto driving once we turn him on in climb and I can’t think of a reason they’d disconnect it multiple times in the climb other than if something was acting up.

 

[KLB]

I’m also curious about the multiple autopilot disconnects they had prior in the climb. Im certainly not mr super pilot but i and everyone else I fly with leaves Otto driving once we turn him on in climb and I can’t think of a reason they’d disconnect it multiple times in the climb other than if something was acting up.

There is no reason for it. They could have noticed trim issues in the climb out and tried to fit it by manually trimming it instead if letting the autopilot trim it. The autopilot will disconnect if you hit the trim button. Or the autopilot detected an issue and automatically disconnected itself. I'm wondering if they were getting multiple autopilot fail cas messages and continued to re-engage it.

 

[CFI A&P]

I’m also curious about the multiple autopilot disconnects they had prior in the climb. Im certainly not mr super pilot but i and everyone else I fly with leaves Otto driving once we turn him on in climb and I can’t think of a reason they’d disconnect it multiple times in the climb other than if something was acting up.

Also depends on which vertical mode they were using. Like many other autopilots, if you’re using vertical speed, the machine isn’t concerned with IAS. Typically goes like this: Sets 2,000fpm for climb. Approaches or over speeds - crap! Disconnect, regain airspeed control then re-engage and try FLCH or pitch (my preferred mode).

 

[Roger Roger]

Also depends on which vertical mode they were using. Like many other autopilots, if you’re using vertical speed, the machine isn’t concerned with IAS. Typically goes like this: Sets 2,000fpm for climb. Approaches or over speeds - crap! Disconnect, regain airspeed control then re-engage and try FLCH or pitch (my preferred mode).

What kinda cavemen be out there climbing in VS mode

 

[ahw01]

What kinda cavemen be out there climbing in VS mode

Just like a Cessna!

 

[KLB]

What kinda cavemen be out there climbing in VS mode

We do VS or pitch mode most of the time while climbing. The plane has too much power to use FLCH mode with power increases. The autopilot can't keep with it and it ends up chasing the speed.

 

[mikecweb]

What kinda cavemen be out there climbing in VS mode

These days, fairly often. 3500FPM in the 30s I'll V/S to 1500 and then 1000 for level offs.

 

[gotWXdagain]

Preliminary report for the initially reported “turbulence fatality” from earlier this month just released. Turns out, nothing to do with turbulence and a lot more going on than was initially believed (shocker).

https://s3.documentcloud.org/documents/23722207/report_era23la135_106816_3_24_2023-10_09_31-am.pdf

“The flight crew reported that around 6,000 ft, they observed multiple EICAS caution messages. The crew recalled EICAS messages of ‘AP STAB TRIM FAIL’ [autopilot stabilizer trim failure] ‘MACH TRIM FAIL’ and ‘AP HOLDING NOSE DOWN’. Neither crewmember could recall exactly what order the EICAS messages were presented. They also reported that additional EICAS messages may have been annunciated.

The PIC asked the SIC to refer to the quick reference handbook. The SIC, via an electronic flight bag (iPad), located the quick reference card and the ‘PRI STAB TRIM FAIL’ [Primary Stabilizer Trim Failure] checklist. The SIC visually showed the PIC the checklist, and they both agreed to execute the checklist. The first action on the checklist was to move the stabilizer trim switch (‘STAB TRIM’), located on the center console, from ‘PRI’ (Primary) to ‘OFF.’ The SIC read the checklist item aloud and he subsequently moved the switch to off.

As soon as the switch position was moved, the airplane abruptly pitched up. The PIC reported that his left hand was on the flight controls and his right hand was guarding the right side of the flight controls. He immediately with both hands regained control of the airplane in what he estimated to be a few seconds after the airplane’s pitch oscillated up and down. During the oscillations, the PIC instructed the SIC to move the stabilizer trim switch back to the primary position, which the SIC accomplished.

…

The airplane immediately pitched up to about 11° and reached a vertical acceleration of about +3.8g. The airplane subsequently entered a negative vertical acceleration to about -2.3g. The airplane pitched up again to about 20° and a vertical acceleration of +4.2g was recorded. The stall protection stick pusher activated during this pitch up; subsequently, vertical acceleration lowered to about +2.2g which was followed by a cutout of FDR data.”


All of this occurring after an initial aborted takeoff due to a pitot cover-induced airspeed disagree, followed by a takeoff with unpopulated v-speeds. Plenty more happening on the ground as well. Certainly a lot going on here…

bUt TwO pIlOts ArE sAfEr

 

[SlumTodd_Millionaire]

And people wonder why I support automation.

Automation doesn't forget to check No-Go Guides. Automation doesn't run the wrong checklists. Automation doesn't forget what annunciators mean.

 

[Roger Roger]

These days, fairly often. 3500FPM in the 30s I'll V/S to 1500 and then 1000 for level offs.

Yeah but you fly an absolute monster

 

[inigo88]

Also, those load factors are uh….above ultimate load factors for a part 25 aircraft in both directions, I think

Thanks for pointing this out. FAR part 25 is generally +2.5 G, and up to -1.0 G. Airworthiness certification requires a safety factor of 1.5 (150%) which would equal 3.75 G ultimate loads. That 150% is for uncertainty in analysis, manufacturing and other unknown unknowns. It is NEVER a buffer meant for pilots to dip into (but as a pilot myself I’m glad it’s there).

Note that since excess structural weight eats into useful load, range and other mission capability, manufacturers get as close to that 150% as possible. When Boeing did their static structural wing test to failure on the 777 wing, they prided themselves on the fact that it failed at 154%.

Not only is this airplane a write off, the rest of them were lucky to make it back to the ground alive.

 

[Roger Roger]

Thanks for pointing this out. FAR part 25 is generally +2.5 G, and up to -1.0 G. Airworthiness certification requires a safety factor of 1.5 (150%) which would equal 3.75 G ultimate loads. That 150% is for uncertainty in analysis, manufacturing and other unknown unknowns. It is NEVER a buffer meant for pilots to dip into (but as a pilot myself I’m glad it’s there).

Note that since excess structural weight eats into useful load, range and other mission capability, manufacturers get as close to that 150% as possible. When Boeing did their static structural wing test to failure on the 777 wing, they prided themselves on the fact that it failed at 154%.

Not only is this airplane a write off, the rest of them were lucky to make it back to the ground alive.

i thought of you when I was making that post.

 

[Roger Roger]

We do VS or pitch mode most of the time while climbing. The plane has too much power to use FLCH mode with power increases. The autopilot can't keep with it and it ends up chasing the speed.

Are you talking about like getting a lot of level offs and then a new altitude in busy airspace so you’re jockeying the thrust a lot? Like when @NovemberEcho calls you right as the autopilot starts to capture with your next altitude, which is 2000’ higher, and repeats until FL180?

 

[MikeOH58]

Thanks for pointing this out. FAR part 25 is generally +2.5 G, and up to -1.0 G. Airworthiness certification requires a safety factor of 1.5 (150%) which would equal 3.75 G ultimate loads. That 150% is for uncertainty in analysis, manufacturing and other unknown unknowns. It is NEVER a buffer meant for pilots to dip into (but as a pilot myself I’m glad it’s there).

Note that since excess structural weight eats into useful load, range and other mission capability, manufacturers get as close to that 150% as possible. When Boeing did their static structural wing test to failure on the 777 wing, they prided themselves on the fact that it failed at 154%.

Not only is this airplane a write off, the rest of them were lucky to make it back to the ground alive.

Good, Challenger operators could use the parts. Dibs on a main wheel assembly and a CMS monitor.

 

[KLB]

Are you talking about like getting a lot of level offs and then a new altitude in busy airspace so you’re jockeying the thrust a lot? Like when @NovemberEcho calls you right as the autopilot starts to capture with your next altitude, which is 2000’ higher, and repeats until FL180?

All climb phases really. It just does a poor job of it. Climb power in the 300 and 250kts gives you 5000-6000fpm on most days and FLCH can't keep up with the trimming portion. FLCH really only works well in idle descents when you slowly pull the power back. So the plane gets into this weird porpoise. It's best to just put it into VS or pitch mode and put it where you want it.

I am curious on how the 3500 handles it all with the autothrottles though. I already here the takeoffs are interesting because it just pushes the thrust levers right up and there is really no lag in these engines at all. It has ti be quite the launch everytime!

 

[Roger Roger]

All climb phases really. It just does a poor job of it. Climb power in the 300 and 250kts gives you 5000-6000fpm on most days and FLCH can't keep up with the trimming portion. FLCH really only works well in idle descents when you slowly pull the power back. So the plane gets into this weird porpoise. It's best to just put it into VS or pitch mode and put it where you want it.

I am curious on how the 3500 handles it all with the autothrottles though. I already here the takeoffs are interesting because it just pushes the thrust levers right up and there is really no lag in these engines at all. It has ti be quite the launch everytime!

Does the 300 have a high speed FLC mode? Something with that kind of thrust 250 seems way too slow for an enroute climb!

 

[KLB]

Does the 300 have a high speed FLC mode? Something with that kind of thrust 250 seems way too slow for an enroute climb!

Enroute climb is 280-300kts. But FLC would just chase the desired speed. It's just about the only poor design of the plane honestly. It's really fun watching the new guys attempt to use it in the climb phase of flight actually. Haha

 

[Roger Roger]

Enroute climb is 280-300kts. But FLC would just chase the desired speed. It's just about the only poor design of the plane honestly. It's really fun watching the new guys attempt to use it in the climb phase of flight actually. Haha

Interesting. My current ride does fine up until Mach transition, then it often oscillates. But it’s weird, sometimes it’ll be just fine all the way to cruise *shrug*