Jeju Air, South Korea

[Rene]

Good article

Jeju Air 737 crashes after attempted gear up landing in Muan | Flightradar24 Blog

Take a closer look at Jeju Air 737 crashes after attempted gear up landing in Muan, learn more about flight tracking and get the latest aviation news with Flightradar24.

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"investigate the embankment"

Yup, that embankment is a might suspicious.

 

[Greg Bockelman]

A possibility I throw out again, could a bird or birds have penetrated the nose of the aircraft triggering damage that shut down the CVR/FDR and other systems? I have seen a single mallard puncture the skin under the captains windshield and cause cockpit damage.

Don’t see how. AFAIK, the only thing there is the radar antenna.

 

[flyingcheesehead]

A possibility I throw out again, could a bird or birds have penetrated the nose of the aircraft triggering damage that shut down the CVR/FDR and other systems? I have seen a single mallard puncture the skin under the captains windshield and cause cockpit damage.

Birds can really mess some stuff up. I wish I'd gotten a front picture of this, but you can at least kinda tell there's a hole in the nose, and it goes back to where you can see the, uh, "extra antenna" hanging out underneath:

 

[flyingcheesehead]

The prelim is out (and attached).

 

[flyingcheesehead]

Looks like they were cleared to land, tower advised caution for bird activity at 8:57:50.

Exactly one minute later, CVR and FDR stopped at 498 feet and 161 knots 1.1nm from the Runway 1 threshold; 6 seconds after that they declared a mayday, so it sounds like it might be plausible that the bird strike caused the recorders to stop.

Both engines had feathers and bird blood stains on them, but both were buried in the embankment so it's probably going to be difficult to be certain to what degree they failed.

 

[35 AoA]

There is a pretty straight forward method to determine if the engines were running prior to ground impact. Has been reliable for decades of mishaps that ended in harder things than a dirt berm. Though like you say, the degree of damage if still operating, might take some more skill on the part of the investigating team

 

[Bacho]

A possibility I throw out again, could a bird or birds have penetrated the nose of the aircraft triggering damage that shut down the CVR/FDR and other systems? I have seen a single mallard puncture the skin under the captains windshield and cause cockpit damage.

From the power system diagrams posted, the most obvious way for birds to take out the boxes is taking out both engines. I cant imagine how birds could take out both engine generator busses without that. We seem to think one engine was running from the video though.

IMO, the airplane does not appear to have flew through 100,000 birds in the limited view we have. I would expect to see the cockpit area peppered with blood marks if that was three case.

 

[Matthew]

Looks like they were cleared to land, tower advised caution for bird activity at 8:57:50.

Exactly one minute later, CVR and FDR stopped at 498 feet and 161 knots 1.1nm from the Runway 1 threshold; 6 seconds after that they declared a mayday, so it sounds like it might be plausible that the bird strike caused the recorders to stop.

Both engines had feathers and bird blood stains on them, but both were buried in the embankment so it's probably going to be difficult to be certain to what degree they failed.


View attachment 137548View attachment 137549

I noticed that timeline, too. The recorders stopped (and I’m still not sure if it was the recorders or data aquisition that stopped) but they still had electrical power to the radios. The different power systems might also be clues to what was damaged and where.

 

[midwestpa24]

Don’t see how. AFAIK, the only thing there is the radar antenna.

What I am suggested is more than just the radome. Say a bird punctured the skin above the windscreen and took out all of part of the overhead console, where all of the electrical controls are. It seems most are having trouble explaining the total loss of power to the CVR/FDR, even from a dual engine loss. Just looking for other explanations.

My other speculation is that they took the bird strike just before or after the decision to go around. They obviously had running engines at the time of the go-around, but I would guess lost thrust to one or both necessitating what appears to be a deadstick approach from the opposite direction. One question that may remain unanswered due to the loss of the CVR/FDR data is whether the loss of thrust was caused by damage or pilot input.

 

[Larry in TN]

A possibility I throw out again, could a bird or birds have penetrated the nose of the aircraft triggering damage that shut down the CVR/FDR and other systems?

The flight recorders are in the tail.

but they still had electrical power to the radios.

In a loss of both generators, you have electrical power to the radio--singular. The No.1 comm radio is powered by one of the battery busses and uses the upper antenna, so a gear-up landing won't take it out.

Say a bird punctured the skin above the windscreen and took out all of part of the overhead console, where all of the electrical controls are. It seems most are having trouble explaining the total loss of power to the CVR/FDR, even from a dual engine loss.

The flight recorder power is not routed through the overhead panel.

It is not difficult to explain the loss of power to the recorders when both engines are damaged. When you lose both generators, you will lose power to the flight recorders.

I would guess lost thrust to one or both necessitating what appears to be a deadstick approach from the opposite direction.

You can't stay airborne for four minutes when you lose both engines around 500' and 161 knots. They also wouldn't have had time to retract the flaps, likely Flaps-30, that they would have had at ~500' on Final. Clean maneuvering speed, depending on weight, would be in the 190kts to 210kts range.

One question that may remain unanswered due to the loss of the CVR/FDR data is whether the loss of thrust was caused by damage or pilot input.

What evidence do you have that suggests the pilot's shut down the engines?

 

[AV8R_87]

Say a bird punctured the skin above the windscreen and took out all of part of the overhead console, where all of the electrical controls are.

Plausible. There was a helicopter accident years ago in LA where a bird hit just right to smash through and pull the throttles back to almost idle. In the ensuing mayhem the crew failed to realize it in time and the autopilot drooped the rotor beyond what was recoverable.
That is a lot of electrical failures to be triggered simultaneously, though. Electrical busses and controls have to have some degree of separation to ensure that an electrical fire or some other fault doesn't take out the entire electrical system.
I'm still thinking the loss of electrical power was triggered by engine failures, with the crews potentially pulling the fire handles.
My only unexplained issue is that, based on what Larry in TN is telling us, loss of both generators should still keep the CVR going. But (and here I'm speculating) in some installations CVRs and FDRs are powered from a battery bus and a generator bus, for redundancy. If this was the case here, there is a chance the power feed from the battery bus was faulty and nobody noticed it. It only became a problem when both generators dropped offline.

 

[midwestpa24]

You can't stay airborne for four minutes when you lose both engines around 500' and 161 knots. They also wouldn't have had time to retract the flaps, likely Flaps-30, that they would have had at ~500' on Final. Clean maneuvering speed, depending on weight, would be in the 190kts to 210kts range.

As I said in the other part of my post you quoted, they obviously had thrust at the point of go around. At some point after the go around, we assume by the apparent gear up, deadstick appearance of the landing they lost thrust to one or both engines, either due to the bird strike damage or crew action. Without the data recorders, it may be hard to determine that.

 

[Matthew]

The flight recorders are in the tail.


In a loss of both generators, you have electrical power to the radio--singular. The No.1 comm radio is powered by one of the battery busses and uses the upper antenna, so a gear-up landing won't take it out.


The flight recorder power is not routed through the overhead panel.

It is not difficult to explain the loss of power to the recorders when both engines are damaged. When you lose both generators, you will lose power to the flight recorders.


You can't stay airborne for four minutes when you lose both engines around 500' and 161 knots. They also wouldn't have had time to retract the flaps, likely Flaps-30, that they would have had at ~500' on Final. Clean maneuvering speed, depending on weight, would be in the 190kts to 210kts range.


What evidence do you have that suggests the pilot's shut down the engines?

Do the engines have to be producing thrust to drive the generators? Or can they be spooling down and still run the generators? Is there a minimum engine power where the generators stop working?

I have to look back at the video: I think it showed one engine, the right engine, ejecting a puff of smoke that has been said to be the moment birds were ingested. But my memory is that there were flaps but no gear at that point. At what point of the first approach would gear have been extended? Or is that engine damage AFTER the left engine was damaged and gear was already retracted for a go around?

 

[Bill]

IMO, the airplane does not appear to have flew through 100,000 birds in the limited view we have.

No, but how many of those birds does it take to kill an engine? Certainly not 1, but 2? 6? 18.3?

Sully didn’t hit 100,000 birds either, but he certainly hit enough to take two engines offline simultaneously.

 

[Larry in TN]

Do the engines have to be producing thrust to drive the generators? Or can they be spooling down and still run the generators?

The generators drop offline almost immediately. They are 3-phase, 115v/400Hz generators. Windmilling isn't going to keep them going. The generator control unit will trip the field relay as soon as the Hertz start to drop.

ejecting a puff of smoke that has been said to be the moment birds were ingested. But my memory is that there were flaps but no gear at that point.

What the video showed were compressor stalls. They could have been at the moment of ingestion, or from the damage from the ingestion as the engine continue to try to run

At what point of the first approach would gear have been extended? Or is that engine damage AFTER the left engine was damaged and gear was already retracted for a go around?

Gear is typically extended roughly 2,000' above touchdown +/- a bit. The normal sequence is...

Flaps 1
Flaps 5
Gear Down, Flaps 15
Flaps 30
(Flaps 40, if used)

Final flaps would normally be set no later than 1,000' above touchdown.

When a go-around is initiated it is...

[Press TOGO] Going around, Flaps 15, check thrust
Positive rate, gear up, set missed approach altitude
Flaps 5
Flaps 1
Flaps Up, After takeoff checklist

Is seems that the go-around, and the bird strikes were in the 400' to 600' range so they should have been fully configured. You don't end up retracting to Flaps Up until accelerating through Flaps 1 Maneuvering speed on the go-around. That would be in the 190kts range, depending on weight.

No, but how many of those birds does it take to kill an engine? Certainly not 1, but 2? 6? 18.3?

One bird, if it's big enough and does enough damage. If the bird is small enough, it might not do any damage at all (to the engine).

Here's a video with compressor stalls from a bird strike. That was a single bird. The engine kept running, sort of, but was having repeated compressor stalls.

 

[david.h]

I work at an MRO and have seen my share of bird strike engines A big flock hitting both engines would be the recipe for this for sure.

 

[tjfelles]

Elementary question... But do control inputs still work with both engines out, no electrical, and no hydraulics?

 

[Larry in TN]

Elementary question... But do control inputs still work with both engines out, no electrical, and no hydraulics?

Of course. Some form of backup is required.

On the 737, you have manual revision. Handles like a truck, but you can still fly it. Other airplanes have a ram-air turbine that drops and provides hydraulic pressure for the flight controls.

 

[skyking3286]

Still thinking is a crew over reaction. Having both engines spool down at the same exact moment makes those fire handles seem more probable. You would think one of the engines would stop later than the other.

 

[Lindberg]

Still thinking is a crew over reaction. Having both engines spool down at the same exact moment makes those fire handles seem more probable. You would think one of the engines would stop later than the other.

Why do you think they both stopped at the same time?

 

[midwestpa24]

Still thinking is a crew over reaction. Having both engines spool down at the same exact moment makes those fire handles seem more probable. You would think one of the engines would stop later than the other.

While we can't rule out crew reaction as a cause to this event, I'm a little skeptical an engine shutdown triggered the loss of electrical power. The electrical power to the FDR was cut right about the point the go-around was initiated, yet the aircraft managed to climb out from that point. I can't imagine that would have been possible with no thrust. With the lack of available information, the timing doesn't seem to add up.

 

[Larry in TN]

Still thinking is a crew over reaction. Having both engines spool down at the same exact moment makes those fire handles seem more probable. You would think one of the engines would stop later than the other.

Why? What is there to gain by pulling the fire handles while airborne? They don't do anything that will help you get the airplane on the ground safely.

Pulling the fire switches first isn't even how we shut down an engine in-flight.

Shutting down both engines in-flight is not something that we are ever trained to do. The training, the memory items, and the checklists are all focused on restoring power, not securing the engines. There is no prop to feather. The airplane does not fly any better once the engine(s) is secured.

LOSS OF THRUST IN BOTH ENGINES (memory items)

1. Engine start switches (both) ... FLT
2. Engine Start levers (both) ... CUTOFF
3. When EGT decreases
.......Engine start levers (both) ... IDLE detent

Steps 2 and 3 are repeated until thrust is regained in, at least, one engine.

Maybe they did something completely random and unsupported by procedures and training, but why would you jump to that conclusion when there is no evidence to suggest it? When you hear hoofbeats, think horses, not zebras.

 

[Ed Haywood]

I still can't get over the stupidity of the black boxes not having battery backup.