Dubious New Technique: Wing-Stop Manoeuvre

31 Mar 17 6 Comments

There’s been a lot of chatter about the Peruvian Boeing 737 which collapsed on landing a few days ago. Obviously there’s not a report yet, but I wanted to try to collect the information so far because three days after the incident. It’s still not clear to me what actually happened.

(Also, I love the dramatic ones where everyone gets out safe.)

Let’s start with the easy details.

On Tuesday, the 28th of March, Peruvian Flight P9-112 departed Lima, Peru for a scheduled domestic flight to Francisco Carle Airport in Jauja. This was a new route for the carrier, with the Lima-Juaja service starting just two weeks earlier. The aircraft was a Boeing 737-300, registration OB-2036-P. There were 141 people on board.

The aircraft departed Lima normally at 16:03 local time for the short-haul jump to Jaua, 170 kilometres (100 miles) as the crow flies. At 3,363 metres (11,034 feet) above mean sea level, Jauja is a high-altitude airport. Runway 13/31 is 2,810 metres (9,220 feet) long.

The weather that day was clear with scattered clouds. The local METAR did not include wind information but, based on the videos below, runway 31 was suffering from a tailwind.

The approach proceeded normally; however as the aircraft touched down on runway 31 at 16:40 local time, something went wrong and the aircraft swerved to the right before veering off of the runway.

Here’s a passenger video of the landing. I’ve skipped ahead to a few seconds before the Boeing touched down (two minutes twenty seconds into the video):

This is where things get a little bit confused. The following all happened but the sequence of these events isn’t quite clear: the aircraft departed the runway. The nose wheel and main gears collapsed. Fuel leaked from the starboard wing and ignited.

Certainly, the aircraft burst into flames. The burning aircraft skidded a short distance after leaving the runway and then came to a halt.

All passengers and crew were evacuated and the fire was extinguished. The aircraft was destroyed. Twenty-nine people were injured and taken to hospital.

Here’s a video taken at the airfield which shows the burning aircraft and the evacuation.

So, a happy ending for everyone but the Boeing.

What isn’t clear is what happened at touchdown: What broke and why did the aircraft swerve to the right?

The final approach, at high altitude with what seems to be a relatively strong tailwind, would have had a high rate of descent. But there’s been no useful information as to the sequence of events (landing, departure from runway, gear collapse, wing impact), in terms of what actually happened at touchdown vs after they veered off of the runway.

Peru’s Ministry of Transport and Communication kept it simple, reporting only that the aircraft OB-2036-P had had a hard landing at Jauja Airport. But I have to say, based on that passenger video, the landing didn’t look very hard to me.

The best information we have on this is from yesterday, when the captain of the flight spoke to a reporter at the Peruvian Portal de Turismo about the landing:

“The runway had nothing to do with it. There seems to have been a technical fault. Until we touched down, everything was normal…I tried to stay on the runway but the pull of the plane to the right was too strong for me. ”

My other question is, what did the starboard wing strike which breached the fuel tank?

CORPAC, the airport authority, reported that the right-hand wing of the aircraft impacted the perimeter fence which caused the fire.

At the same time, Peruvian media said that based on passenger accounts, the wing struck the runway as they were landing.

Finally, the Interior Minister topped it off by explaining that the pilot intentionally dragged the wing along the runway to slow it down.

“The plane couldn’t stop on the runway and they made a manoeuvre to stop it with the wing and that appears to have caused the fire.”

I find it difficult to imagine the manoeuvre to stop a 737 with the wing, let alone the pilots who would attempt it…

The investigation has started and hopefully the aviation authorities will release an early statement explaining what happened here, both on touchdown and after the aircraft left the runway.

In any event, it’s great that passengers and crew are all safe. Shame about that poor little 737, though.

PS: Hurray, sending updates by email is working again! Er, if you didn’t get this, let me know… :)

6 Comments

  • There may well be several factors that caused this incident.
    Tailwind? Once the tailwind component exceeds 10 kts, there are no performance data any more. So stopping distance is unknown but also go-around can be compromised.
    Then the thin air may have been a factor. I just looked it up, the elevation is about 11.000 feet. That means that the cabin must be de-pressurized and the oxygen masks de-activated before landing. Otherwise they would deploy.
    The runway at that altitude is marginal.
    The lift is less in thin air (obviously) and the aircraft will stall at a higher speed. The aircraft will need to fly at a higher speed but the decisive factor is indicated airspeed. The aircraft’s pitot tubes will need the same pressure to register the same speed. In the thinner air that means faster. Faster relative to the ground. So even if the airspeed indicator registers, say 140 kts, the aircraft may well travel at 160.
    Add a bit of tailwind – and if it is correct that the tailwind was “strong”, then the aircraft may have been travelling at a very high ground speed when landing. The approach on final may not have shown a dramatic angle, but the rate of descent may well have been higher than normal.
    Aircraft tyres are rated for a certain maximum speed. This company flies in and out of high airports routinely, perhaps there was stress built up in the carcass of the tyres, perhaps a”blow-out” on the right caused the aircraft to swerve? At high speed this might well have been difficult to control. It could explain why the wing was low.
    Braking with the wing? Nonsense. The engine would scrape along the runway first.
    No, a strange incident but nobody was killed.

  • Many decades ago in 1979 I crewed Carvairs and a couple of times the brakes seized upon retracting the gear. On landing the bottom of the main wheels on the affected sides were totally ablated. At touchdown we slewed across the runway, but not with such dramatic outcomes.

    I suspect maybe there was some sort of brake failure which slewed it off to the right into wet soft dirt and the rest was history. A large aircraft will sink knee deep into ground solid enough to support a truck.

  • Simon, you may be right. But for those who don’t know the Carvair: it was a DC4 with a bulbous nose, a modification if you like, to accommodate large cargo doors in the front with the cockpit above.
    WW2 technology. Personally I have never heard of a 737 wheels seizing on retraction. Personally to me it could be that the tires failed. The 737s of this company were routinely making landings at high altitude. The tyres must have been under higher stress than normal. Landing at the higher speed, on a runway that at this altitude would have been marginal would have required a fair amount of braking. So I think that it is well possible that the tyres were already stressed before, perhaps this was once too many, a tyre blown out puts all the load on the other so it goes as well in sympathy. Two tyres burst on the same side may well explain this incident. But then, we don’t know yet it may well have a different cause.

  • … Besides, if a pilot were to decide to try and stop a large aircraft by digging a wingtip into the surface, doing that whilst travelling at high speed down the runway, it would more than likely result in the aeroplane cartwheeling. Which probably would have resulted in a high number of casualties. The wing would have broken up, spraying fuel all over the place. The fuselage would also break into sections. The fan section of the engine of a B737 is very big and the engine hangs very low under the wing. It would have hit the ground first, causing sparks to fly. The people in the aircraft would have been totally disorientated when the fuselage was spinning around, chairs would have been broken off the floor obstructing those who were trying to get out.
    Ever seen a TV series “Mythbusters”?
    I declare the myth that an aircraft can be successfully halted by forcing a wing into the ground hereby BUSTED !

    • I agree…. I can’t imagine anyone thinking that dragging a wing as a way to stop an aircraft is a good idea. I’m old enough to remember United 232, and from everything I’ve read, they almost made the landing, but one of the wings dipped and hit the ground, which caused the aircraft to cartwheel and break up.

      I’d think that alone would have completely discouraged using a wing to slow/stop an aircraft…..

  • From a very layman’s observation, I somehow feel that the landing speed seems a little too high when compared to other normal landing videos. Not sure if this is due to the video itself or was the real cause as mentioned above by Rudy Jakma

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