Large cargo plane crashes east of Houston

originally posted by: Zaphod58
And the mystery deepens. The aircraft was cleared to divert around weather, but was told that the diversion would require an expedited descent to 3,000 feet. They leveled off at 6200 feet, followed by a brief climb to 6300 feet. At that time the aircraft was showing "small vertical accelerations consistent with the airplane entering turbulence".

The aircraft settled to 230 knots indicated, at which point the engines throttled to maximum power, the nose briefly pitched up to 4 degrees, before an elevator deflection put the aircraft into a nose low position, until they reached 49 degrees nose down until impact.

www.flightglobal.com...

[I]That sounds increasingly like a FCS problem...

a reply to: RadioRobert

I'm sticking with frozen elevator controls.

They're having fun confusing the issue.

While there is no confirmation from the NTSB on what caused the crash, the data from the FDR and the ADS-B both imply that the aircraft entered turbulence, which was consistent with the pilots’ input to push the throttles to full power, this is a standard procedure for all pilots when they enter turbulence and the planes steady climb of 4 degrees nose up is consistent with this input.

airwaysmag.com...

A number of pilots that I've been discussing this with all agreed that going to full power in turbulence as SOP is news to them.

a reply to: Zaphod58

Not uncommon. Not "standard procedure" , but minimizing one's time in the problem area (and/or climbing out of it) is a pretty common reaction. Sort of depends on a lot more of the circumstances than simply "turbulence". Fuel state, relative altitude to the weather or if it's driven by terrain, what portion of the flight you are in, severity of the turbulence or just light chop, structural limitations, etc all factor in. Seems odd given they were at the tail end of the leg and descending, with an ATC suggestion for an expedited descent to avoid the weather.

If you get bad sensor data (icing in the weather?) combined with the FCS mode trying to "protect you", you might get auto-throttled up and an uncommanded nose over. If there is some confusion over what is causing this in the cockpit, you might be in trouble before you can recognize the problem. Then at lower altitude, you get a thaw and the computer finally gets good data, but you're in too deep in a bad spot in the envelope. Might account for the eventual (insufficient) pullout. Simply ran out time/altitude.
Just thinking aloud. Haven't really studied any of the data other than vaguely following the story.

a reply to: RadioRobert

According to the report they were 20 degrees nose down at impact, and were slowly recovering.

a reply to: Zaphod58

Right, they were slowly righting the ship, but in a high-speed dive and a relatively massive airplane, you've got a lot of momentum to overcome. P=M*V Consistent with the computer finally getting good airspeed/attitude data after a thaw. Or letting it get away from you while trying to diagnose the problem. Depending on the weather, they might not have even noticed the magnitude of the nose -down attitude if they're getting bad data on the instruments until you clear the weather and get eyes on the horizon.


Wonder if dropping the gear and small flap input would have mattered any. Overstessing the gear or flaps, even to the point of structural failure, would have brought the drag way up, and the velocity down. Might have bought them enough time to pull out. Real easy to say and think outside the box in the comfort of my chair and already knowing the outcome.

originally posted by: Flipper35
Funny that should come up as the MCAS is designed to prevent pitch changes with power on the 737 MAX due to the engine configuration change.

Sounds a bit like a deep stall and didn't have enough room to correct. (In the story it stated the nose came up to 20* nose down attitude)

You are correct as to the design goal of the MCAS system. But the system relies on inputs from the angle of attack measurement system. People tend to relate aerodynamic stalls strictly to speed and that is incorrect. An airfoil will stall at some critical angle of attack regardless of speed. I'll give an example. I fly competitive aerobatics. The fifth figure in this year's Unlimited Compulsory sequence is a tailslide with a snap roll on the vertical downline. This means you fly a perfectly vertical upline until the aircraft stops and then slides backwards until you use the elevator to get the nose pointed straight down with full power. The aircraft never stalls on the upline, even with zero airspeed but does stall at full power going straight down at at least 3 times the normal straight and level stall speed. You must stall the wings to do a snap roll. The MCAS on the Max is designed to assist in preventing stalls by using down stabilizer trim to reduce AoA if it gets near critical. The Lion Air Max that crashed in Indonesia had a malfunctioning AoA system that was indicating 20 degrees positive AoA on the captain's side. I can't answer exactly for the Max8, but most jet wings have a critical alpha of 14-16 degrees. You can disable the MCAS system by flipping two switches on the center console next to the engine start switches. I don't think the MCAS is inherently dangerous if the inputs are correct and aircrews are sufficiently trained.

originally posted by: Zaphod58
a reply to: Flipper35

They eventually reached 49 degrees nose low. They're hoping to release the CVR transcript soon, but there was some trouble with that one.

Sorry I wasn't clear. They were back to 20* nose low after 49* nose low like they were recovering from a stall.

One of my flight instructors used to be a test pilot for McDonnell Douglas. One of his worst flights they took the new at the time DC-10 up to 36,000' and stalled it. They recovered from the spin at just under 10,000'. Jay Miller (pilot, not the author)

So, two days ago it was SOP to go to full throttle in turbulence. Tonight, they're looking at pilot error and believe the pilots inadvertently advanced the throttle to full throttle.

originally posted by: Zaphod58
So, two days ago it was SOP to go to full throttle in turbulence. Tonight, they're looking at pilot error and believe the pilots inadvertently advanced the throttle to full throttle.

I don't believe that it has ever been the SOP to go full throttle if you encounter turbulence. In fact, the Boeing manual for the 737 states that upon encountering turbulence, you set thrust at whatever N1 (engine fan speed) to the VB N1 as set up in the FMC. Usually, that means reducing N1 by 1% or so. If you are cruising along at 41,000 feet and run into turbulence and you go full thrust, you will overspeed (exceeding Mach .82) and run the risk of encountering mach tuck, tirst shedding the tail, followed rapidly by the wings. You then become a 100,000 pound lawn dart. Now, it is SOP to go full throttle if you encounter a microburst downdraft on approach. You go full thrust and pull back on the yoke until you're in stick shaker and you continue to fly in shaker until you start climbing. This is the procedure worked out after Delta 191 in Dallas.

a reply to: F4guy

I know it isn't, but the previous articles published about the NTSB report made that claim.

According to information released yesterday by the NTSB, there was a complete breakdown of CRM (color me shocked), and the first officer had no business in the cockpit of any aircraft.

The first officer failed proficiency testing at Atlas, who operates the flights for Amazon, as well as at Mesa, and had washed out at two other airlines. According to documentation from Atlas, he told them he was working freelance real estate and taking college courses during that time.

He was at the controls during the descent, and told the captain that his PFD wasn't working, and there was a problem with his HSI. He turned control over to the captain, but control was turned back over after his display appeared to be working again. As they descended through clouds, the Go Around switch was activated. The first officer stated that they had stalled, and reacted by pushing the nose down to recover airspeed. The captain began pulling back on the control column to try to bring the nose up, but the first officer didn't help him until they were below the clouds, after it was far too late.

Source

www.flyingmag.com...

a reply to: Zaphod58

m.youtube.com...

This ones hard to watch. Poor airmanship overall and especially knowing that the FO had no business in the right seat of that jet (or any jet).

originally posted by: Zaphod58


Fire, stall (although unlikely), hydraulic or another system failure, structural failure....

30k per min is like no wings.... Hell even 6k is not easy.

a reply to: justwanttofly

Yeah, that was pretty bad. Thank God it was only a cargo flight though.