HouseOfPAE

Summary: UAL 777-200 departed OGG and soon experienced an 8,600 FPM descent, coming within ~800 ft of the surface before successful recovery.
Saw this in the news today: United dive after Maui departure adds to list of industry close calls - The Air Current and also picked up by NBC News: United Airlines plane taking off from Maui plunged to within 800 feet of the Pacific Ocean, flight data shows (msn.com)

JohnBurke

An 777 on departure, having reached 2,200', entered an 8,600 fpm dive, recovered after a descent of 1,400', and then began climbing at 8,600 fpm?

Not buying it.

Curious that the descent rate and climb rate are reported to be the same values. I'm not a big believer in coincidence.

A transition to a descent at 8,600 fpm would require a significant unloading of the wing; perhaps someone can figure the math, but I can't see how it wouldn't b negative, and then after a short descent, only a 2.7g recovery? How does the 777 achieve a climb of 8600 fpm? They're getting this from the clear and definitive Flight Radar 24?

hopp

A 2.7g pull up could cause a momentary 8600fpm climb rate to be reported.

AirBear

Article from SimpleFlying.com: UAL said:

“After landing at SFO, the pilots filed the appropriate safety report. United then closely coordinated with the FAA and ALPA on an investigation that ultimately resulted in the pilots receiving additional training. Safety remains our highest priority.”

https://simpleflying.com/united-airl...scends-775-ft/

rickair7777

8,600 could be the limit of the VSI and/or FDR?

You can easily get 3000+ fpm on a normal climb out at sea level and that's just with pitch set, not pulling any G's.

There's a thread on this in the UA forum...

OGG nose dive...woah!

JohnBurke

Reportedly the descent began after reaching 2,200' on the climb-out; descent ended at 775' and lasted 21 seconds. This equates to a descent rate of 68 feet per second, or 4000 fpm.

A descent rate of 8600 fpm is 143 feet per second, and in 21 seconds, is a descent of 3,000', effectively putting the airplane 800 feet underwater.

https://edition.cnn.com/travel/artic...aii/index.html

Of course, the entire descent could not be at 8,600' as acceleration is not instantaneous. This indicates, if the numbers are to be believed, the descent at some point achieved a vertical velocity of 8600 fps. Increase to that rate, and decrease from that rate to recover by 775' mean that the average rate is much less, meaning information is inaccurate or incomplete, but it's still difficult to swallow that the descent rate was achieved over such a short descent, and also that the same vertical rate was achieved on both descent, and the subsequent climb. The only explanation I can imagine, other than pure coincidence (which I cannot believe) for identical clim and descent numbers would be as Rickair7777 suggested; the limit of the recording device (or reporting system). Still, if the time interval is known (21 seconds), and the distance traversed is established (1,420'), then it's not much of a math problem to determine that 68 feet per second is half the advertised rate of 143. Also, the airplane was never underwater...

aaatwood

The avherald article is useful. http://www.avherald.com/h?article=50526a09&opt=0

Dooder

The 8,600 FPM may be a red herring, a data artifact.

This feels like a low airspeed, high AOA event that went a bit too far.

hydrostream

Hand flying or thinking the autopilot is engaged and both heads getting sucked into the radar/FMS/etc, not noticing the unusual attitude. That's my guess based on my own past errors.

rickair7777

AVHerald is wrong that 2.7G's would require NTSB notification. It would require an inspection... if serious structural damage was found, THAT might require notification. But I doubt 2.7G' would damage anything clean, or even with a low flap setting. Full flaps maybe, but they apparently only had one notch out when this went down.