1977 Tenerife accident - avoidance

[FlightDream111]

Another one from the Spectators' Balcony and Spotters corner:

Novice question here:

The Tenerife accident has been discussed here before. I have glanced through through the accident report, however I cannot ascertain the following, out of curiosity, maybe some of the pilots here could answer the following:

1) Could the accident have been avoided if the KLM pilot aborted the take off as soon as he saw the other aircraft - brakes, reverse thrust, turning off the runway at high speed etc. As far as I know they saw each other 9 seconds before impact.

2) What it the Pan AM pilot used reverse thrust instead of trying to turn off the runway? Would it have made the difference is 20 ft that was needed for KLM to clear the Pan Am 747?

Is is possible? ( V1 was called 4 seconds after the PAN AM pilot saw the KLM 747)

V1 speed (http://en.wikipedia.org/wiki/V1_speed), the maximum speed at which an aircraft pilot may abort a takeoff without causing a runway overrunApart from human factors, could suitable accident avoidance procedures have made the difference?

I mean no disrespect to any of the flight crew or companies involved, just curious.

Transcript part from Wikipedia:

1706:40.0
[Pan Am captain sees landing lights of KLM Boeing at approx. 700 m]
PAN AM CAPTAIN There he is ... look at him. Goddamn that son of a bitch is coming!
PAN AM FIRST OFFICER Get off! Get off! Get off!
1706:43.4
KLM FIRST OFFICER Vee-one.
1706:44.0
[PH-BUF (KLM 4805) started rotation.]
1706:47.4
KLM CAPTAIN [Exclamation/expletive]
1706:50
N736PA (Pan Am 1736) records sound of collision.

[Cymmon]

No, and does it matter?
This has been done to death....

[DaveReidUK]

Apart from human factors, could suitable accident avoidance procedures have made the difference?Before asking a question like that, you would have to define what you mean by "suitable accident avoidance procedures".

If "accident avoidance procedures" are procedures that avoid accidents, then you would appear to have answered your own question.

[+TSRA]

At the risk of starting [another] debate, I'll throw my 2c in for your first question, although having never flown a 747, I would only be speculating whether they could have used reverse thrust. My gut says no considering much more thrust is produced in the forward thrust range than the reverse thrust range and therefore more thrust to move the weight...


The answer to your first question requires some background. The CVR tape indicates that the words spoken at 17:06:47 were "Oh ****" and that this was recorded from Captain Veldhuyzen van Zanten (KLM). While this may indicate this is the point at which he realized they would not climb over the Pan Am aircraft, it is generally accepted that it was when the KLM crew were able to see the Pan Am 747.


The interviews with the Pan Am pilots indicate they first saw the landing lights of the Dutch 747, not the aircraft itself (this is shown in your quote in the first line). The Pan Am pilots would have been watching the landing lights approach for a couple of seconds before they saw the aircraft itself. The Dutch pilots, on the other hand, would not have seen any lights through the fog as it is likely Pan Am only had a taxi light on - typically not bright enough to shine through dense fog. Therefore, the Dutch pilots did not have 9 seconds to respond, they had at best six seconds, at worst three seconds.


Now, as for your question: Could the accident have been avoided if the KLM pilot aborted the take off as soon as he saw the other aircraft - brakes, reverse thrust, turning off the runway at high speed etc. As far as I know they saw each other 9 seconds before impact.

No. Even in the best case scenario of 9 seconds, this would require the pilots to identify the threat, apply the correct actions, and stop a loaded aircraft as heavy as a 747. It would have been impossible given those conditions. There was simply not enough runway length available. You asked about a high speed taxiway, and while there was one, it would have come after the point of contact.


I'll avoid talking about V1, because that will simply open up thread drift to something called Balanced Field Length among other things...it's just not worth it. http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/badteeth.gif PM me if you want to have that discussion.

[akerosid]

Not directly relevant to your question, but here's an interesting article from the Dutch media from the perspective of Capt Van Z's family:

Een handbreed gesteld - Digibron.nl (http://www.digibron.nl/search/detail/01357741511a0642eec56cc7/een-handbreed-gesteld)

Your browser can be set to translate into English; not a brilliant translation, but understandable anyway.

[Burnie5204]

Indeed

Even if the KLM Captain had seen the Pan Am sooner there is the decision to take:

1 - Cut the throttles, apply reverse thrust and DEFINITELY hit the Pan Am due to lack of stopping distance

OR

2 - Apply additional thrust (if available) to get to Vrotate and POSSIBLY hit the Pan Am but POSSIBLY climb over it in the distance available.


One has Zero chance of avoidance, one has potential to be entirely injury free.


However, the KLM didnt see the Pan Am until too late to even think about making the decision let alone act on it.

[FlightDream111]

Thanks for the article, Google has outdone itself this time:

From that moment came a circuit of alleged facts and rumors started that, like the disaster itself, is unparalleled. It continues to the present day, and the amount of often contradictory theories, speculations and experts statements increasing rather than decreasing

[FlightDream111]

Thank you for all your replies:

Thrust reversal - on the Pan Am 747, instead of increasing power and swerving to the right, how many feet would it have been gained - in terms of clearance by simply applying full reverse thrust without turning?

I take the point that the KLM Captain saw the Pan Am 747 later, however there was enough time to respond and drag the tail on the ground for a distance.

I accept that collision may have occurred, however what if the KLM selected reverse thrust, and applied full brakes (maybe full flaps - no time) . How much would they have slowed down in 4 seconds or whatever time available and would this have collapsed the gear if a slight deviation was applied - going off runway despite all consequences , accepting that this is a non-intuitive move at best?

Maybe the KLM Captain chose the best option?

[AerocatS2A]

I think it is hard to say what would have been the best option. There were no good options, and there was no way of avoiding the impact once the take-off was commenced. In one case you clip the top of the PAN-AM while you are flying or nearly flying, this is really bad for the KLM aircraft but not necessarily as bad for the PAN-AM, in the other case you collide on the ground at a slightly slower speed. This would probably result in a better outcome for the KLM but worse for the PAN-AM. Almost everyone died anyway, who knows if maybe a few extra would have survived (or been killed) if a different option was chosen.

From a personal point of view continuing the take off probably gave the pilot of the KLM a small apparent chance of survival, while stopping would've have ensured collision and given him no chance of survival (first on the scene of the accident and all that.) So from the point of view of the pilot, without the benefit of hindsight and considering personal survival only, the continued take-off was likely the best choice.

[Bergerie1]

I have flown 747s with P&W and RR engines. In answer to whether the PanAm pilot could have used reverse thrust - the answer is no. Applying reverse thrust above a very low power level when the aircraft is stationary causes the engines to surge. They then need to be shut down.

[Skipness One Echo]

However, the KLM didnt see the Pan Am until too late to even think about making the decision let alone act on it.
The KLM crew saw the Pan Am and rotated early, scraping the tail and just getting airborne prior to impact. There was no chance to stop or get out of the way given the thick fog.

You can't reverse a heavy using reverse thrust.

[+TSRA]

take the point that the KLM Captain saw the Pan Am 747 later, however there was enough time to respond and drag the tail on the ground for a distance.



Not sure why "quote" isn't working for me.


I believe you are mistaking V1 for VR. Just because the KLM crew past the speed at which point a decision about continuing the take-off or rejecting the take-off does not mean that the aircraft was ready to rotate. It is accepted (based on evidence) that the KLM aircraft was indeed "dragging" the tail prior to impact. But this actually makes the situation slightly worse if you try and rotate before the aircraft is ready to do so.


I accept that collision may have occurred, however what if the KLM selected reverse thrust, and applied full brakes (maybe full flaps - no time) . How much would they have slowed down in 4 seconds or whatever time available and would this have collapsed the gear if a slight deviation was applied - going off runway despite all consequences , accepting that this is a non-intuitive move at best?

Take a second to consider what you're asking here. You're asking a crew of a 200-400 tonne aircraft to, in anything between 3 to 6 seconds, select reverse thrust, apply brakes, begin to raise flaps, and turn off the runway. You're not giving these guys any time to come over the shock of seeing their death approaching at 140 knots. You're also assuming that this stuff happens immediately. Thrust reversers take a couple seconds to go from full power to full reverse; it takes a couple seconds to overcome that much kinetic energy.


The questions you're asking are not the right questions. You should be asking how they got into making the decision to go in the first place - not how could they get out of it. Once the take-off decision was made, the accident was inevitable. Ask why the controller allowed two aircraft to taxi down the same runway. Ask what may have contributed to the errors in the decision making. Ask what procedures could have/should have prevented two aircraft being on the runway at the same time. Ask what may have been on the mind of the Dutch Captain. Asking these questions and finding the right information (not that provided by Discovery Channel) allows you to see this accident for what it is, not what it is portrayed as.

[HEATHROW DIRECTOR]

<<Ask why the controller allowed two aircraft to taxi down the same runway.>>

What's wrong with that, unless you are referring to the accident in question?

[awblain]

The controller had intended to allow one aircraft to line up and one to taxi, but used strings of dreadful terminology, on a very stressful day.

The communications and terminology were messed up sufficiently that KLM thought they were cleared to take off.

The communications and terminology continued to be sufficiently messed up that Pan Am got no clear warning that KLM was rolling, and KLM got no notice that Pan Am was still on the runway.

Once the KLM reached about 100kts, corresponding to around half of the impact energy, there was going to be an accident.

[+TSRA]

I did mean that for this specific case Heathrow Director. I did not mean to suggest that a normal procedure should be abolished, but rather that it should have been clear that bad weather was rolling in so how did that affect the decision making of the controller (as well as the pilots). It's been my experience that as soon as the controller can no longer see the runway end (without ASDE) that back-tracking two at once stops.

[glendalegoon]

I offer this:

With the visibility and everything else, this accident probably couldn't be avoided once KLM started the takeoff roll.

I learned from this, don't be in a hurry to takeoff. I've even avoided taking ''immediate takeoff clearances" in certain situations.

I do know a pilot. He was then a copilot on a DC9 about 30 years ago or so. His plane was taking off at KORD, all cleared just fine by ATC. A 727 however managed to get on his runway without the correct clearance.

My friend rotated considerably earlier than V1/VR taking off at minimum unstick speed, going to firewall power and managed to "JUMP" over the 727, saving everyone. He and his captain received the dadelian award from ALPA. A fine man, fine pilot and I'm proud to know him.

What I mean by all of this is you can't just be fat, dumb and happy and never think something bad isn't just a second or two ahead of you. Be ready and ACT.