Incident at Airport Dortmund (Germany)

[IFixPlanes]

I only quote the initial notification at the preliminary report of the BFU (Aktenzeichen 5X001-10).
No assumption from my side. To calm you down i have removed the "no".
BTW i am a mechanic not a pilot.

[lederhosen]

No problem and thanks for making the change. I think both sources add to the debate. The interesting bit for me as a 737 skipper is the go / no go decision making and what I can personally learn from it.

[safetypee]

120 kts appears rather high even for any overswing acceleration for a reject at V1; particularly high for a single ASI fail or miscompare. Any comments, or an approx V1 on the short runway (Re #80).
On what basis is only one reverse used in RTO performance, isn’t it all or nothing (Re #78).

[Brookfield Abused]

Reject at 120 kts on a wet/contaminated/field length limited RWY!

Ok so a reject "initiated" at 120 kts.
Brakes on speed was maybe 125kts?
But with a reduced V1, it may well be at this number or above?
Usually Field Limit ASD (calculated) will stop the aircraft so that the nose wheel is maybe just about to go off the pavement (a few feet prior)!
Next question is what sequence happened after the trust levers were closed to idle?
Were speed brakes manually deployed or extended after thrust lever/s selection?
Were thrust lever/s raised - if yes, when, how much thrust was selected?
IF the Pilot Flying forgot to perform the above sequence, were call-outs made by the PF? What reaction did that bring?
When were the thrust levers lowered?
Was braking performed by the auto-brakes, manually or a combination of?
If you know you be going off the runway - a BRACE BRACE would have been nice to hear!

[lederhosen]

Credit is allowed on wet runway for one reverser as per 737 QRH performance text. The logic is that you have one reverser on a twin if an engine fails before V1.

For Brookfield Abused the 737 has an auto speed brake system which operates when wheel spin up above 60kts, thrust levers idle and reverse selected. These conditions existed.

As I posted earlier the investigator is reported as saying that the performance calculation was OK and the aircraft should have stopped within the runway available.

[Tee Emm]

Looking at the groudspeed given by IRS is not practicable, especially at high speed.

It should be normal procedure at the 80 knot IAS call by the PNF for both pilots to check the ground speed. In any case knowing the wind component the ground speed should be IAS plus or minus the HW or TW component. This is very handy if an ASI problem shows up later in the take off run. There is very little time to assess which airspeed indicator is playing up and experience has shown countless times that a high speed abort on a limiting length will invariably result in an overrun - particularly on a wet runway.

That is where an alert crew will switch to ground speed for lift off. Of course, the pilot has to have some idea what ground speed he needs to lift off safely. That is good airmanship. The 80 knot check in a Boeing is much more of an important safety check than many pilots realise. For instance, if during the take off run the PF does not hear or does not receive the call "80 Knots" from the PNF as the PF airspeed passes 80 knots, it is good airmanship for the PF to call out something like "90 knots my side". Because by the time he realises the other pilot has forgotten to call 80 knots - or for some reason the PNF has not yet reached 80 knots on his ASI, the PF may well have 90 knots or more. By calling his own airspeed after not receiving the expected call-out from the PNF, this gives early warning of a potential problem. But few operators have this policy.

Simulator training in this regard is vital, as it shows out the momentary confusion that will occur when conflicting airspeed indications occur during a take off roll. The secret is to be prepared. Well trained crews should be prepared even though the company SOP may have no mention of erroneous airspeed indication during take off. After all, company SOP cannot foresee every problem that can occur when flying and some responsibility must be borne by the captain to run his ship safely. It is no good falling back on an excuse that there is no SOP.

A couple of years back there was an erroneous airspeed incident to an A330 during take off. The company SOP required a 100 knot call by the PNF as an airspeed comparison check. The captain was unaware that an insect was affecting his ASI. The F/O was PF and as he passed 100 knots he expected a 100 knot call from the captain. It did not occur because the captain's ASI was under-reading significantly caused by the insect blocking his pitot tube and his ASI had not yet reached 100 knots.

The F/O said nothing, thinking the captain had probably been distracted by something and had forgotten to call 100 knots. When the captains ASI finally did reach 100 knots he called it. The surprised F/O then pointed out his ASI was close to V1 whereupon the captain belatedly realised there was an ASI problem - but which one? The captain took control and aborted the take off around V1. The RTO feature worked as advertised and the aircraft stopped safely. During the taxi back the tyres deflated and the brakes were very hot. All this could have been avoided if the F/O had called something like "110 knots my side" when he had not received the captains expected 100 knot call. In that case, if the captain decided to abort, then the speed would have been significantly lower with obvious greater safety margin plus less chance of hot brakes and fusible plus blow. Airmanship is a word that has long since departed from aviation lexicon. Some crews rely 100 percent on company SOP to cover all exigencies when this is patently not good airmanship..

[Avman]

a BRACE BRACE would have been nice to hear!

Maybe, but with a plane load of German tourists? Don't think it would have helped much. In any case, I'd say (from the video) that they slipped off at a very low speed. There was no apparent indication of anything other than a fairly smooth halt.

[Brookfield Abused]

Always try to crash legally!

BRACE BRACE BRACE call??
When these events happen, EVERYTHING is confiscated and reviewed by your company and the Authorities (in this case the LBA) from your briefing to the cabin crew, Tech-log handling and signing, Load Sheet notations/calculations, to your rest period and actions the night before. The best is the Voice Recorder. So when the CVR is combined with the FDR data, everyone who has access- knows what you briefed, any personal comments you made, non-SOP comments or actions, exclusions, etc. Then comes the FDR data which = actions by the pilots and there is no hiding errors.
So if you want to minimize your potential and professional liability - a BRACEx3 call (the pilots had enough time) would have made a very good impression in yet-to-be filled LBA Report which will be 20-30 pages long.
On Field Length Limited T/O's when wet, slippery with a combination of contaminated conditions exists (the worst in my mind and impossible to calculate an ASD), these performance calculations are just that - a computer model which is only a prediction of how a generic AC and crew will behave with standard (JAA) reaction times.
So if the calculated data was correct - then comes the crews reactions and the actual runway conditions. I assume DTM Airport Auth. will have done there BA tests right after the event.
The De-icing Operator will have been interviewed, fluids, hold-over times and his training checked.
Did the Crew accept maybe old and no longer accurate BA data, did they request a new RUN to be done?
Were they in GET HOME ITUS mode? Where they driven by an Airport Closure?
Back to the performance issue.....
In a Rejected Take Off (especially under these conditions) the pilots actions from thrust lever closed, manual speed brake extension together with max. manual/Auto braking, followed by reverser deployment (added decel. bonus) and max thrust spool-up- all must be done without the omission OF ANY ACTIONS or the calculated performance means nothing and for sure you will be doing what they did! With another 10-20 m's of skidding into the Approach Lights metal support frames there could have easily been a fuselage/wing fuel tank breach and fire (plenty of fuel to burn)!
So I come back to the spoiler deployment. Yes, when a reverser is selected the auto-speed brakes are activated and deploy. However, how many times in the sim have I seen people mix and mess these actions up. This comment thread started after watching the video clip from the pax sitting near Eng. 1. We cannot see what the ground and lift spoilers did/deployed when the reject was begun with the thrust levers being closed (reduction in engine sound), but it looks like the reversers MAY have been deployed too late (over 10 sec. after the reduction of the engine sound). Thus the idea that maybe the spoilers extended much later, perhaps not being raised manually right after the Thrust Levers were closed (is a Boeing recommendation).
As far as I know, these performance calculations are made with NO REV THRUST ANYWAYS.
Even if this is just a POSSIBLE sequence of events, it is worth while taking the time to remember just how important these RTO events are ESPECIALLY on this type of short runway with these extreme atmospheric and runway conditions.
Often I see people briefing WE ARE GO MINDED, meaning something like the unreliable airspeed AFTER 80 kts would be taken AIRBORNE with a call from the PIC - CONTINUE, etc! Not a bad briefing idea and execution in hindsight in this case!
So the CRV and FDR will reveal all.
So remember to ALWAYS CRASH LEGALLY and do your job right! The at least you are not to blame!

[safetypee]

Tee Emm, It should be normal procedure at the 80 knot IAS call by the PNF for both pilots to check the ground speed.
I disagree. Even with a pre flight calculation of the expected GS, the accuracy of the wind reports will routinely give a discrepancy. How large can it be, what would the procedure be for handling this error, is it the FMS or the ASI in error, etc, etc.
Pilots should not be faced with such tasks during take off.
Airmanship (company procedure) should establish the essential tasks during takeoff to be balanced by the risk of the operation.
The 80 kt call helps with this; it provides a speed cross check and in many aircraft excludes most systems from any subsequent Go/Stop decision making.
Commercial aircraft have dual or triple airspeed systems, three ASIs. The crew’s task for an ASI disagreement or failure above 80 kts should be simple – which of the three ASIs agree (not which one has failed), use the two systems in agreement to continue the take off.
Do not change or add complexity with more procedures; in doing so you might open other opportunities for error.

How many seconds does it take to read you second paragraph – the procedure words and actions (#86) – in that time how much have you accelerated, how far have you travelled down the runway?

[Jim Croche]

Brookfield
For info, the A320 doesn't have manual lift dumping on the ground during an RTO or landing. The system uses weight on the wheel(s) to give partial or full lift dump. This, in turn, triggers the autobrake to work. If not enough weight on wheels, no spoilers therefore no lift dump and no autobrake and pulling the speedbrake lever will not extend them!! What a lousy system and it's been implicated in numerous accidents and incidents (Garuda, TAM for example).

[A37575]

Airmanship (company procedure) should establish the essential task

You should not make the mistake of confusing airmanship with company SOP. Company SOP is primarily designed to cover litigation. Airmanship takes in the whole picture.

Having observed the erroneous airspeed indication scenario in the simulator literally hundreds of times, we have noticed immediate confusion when an airspeed problem arises during the take off run. With the aircraft accelerating at around 200 feet per second in the latter part of the take off run, there is little time to look at a standby ASI and then compare it with two other ASI's and then calculate which ASI is safer to use. This action would take several eye movements as each ASI is not necessarily adjacent to each other and both the dial scale and needle or drum reading needs to be assimilated. Count on at least five seconds of momentary uncertainty before action is taken.

Remember, it is a different story if the simulator training exercise has been pre-briefed and the crew are aware an airspeed problem during take off is part of the box ticking exercise. In a real life one doesn't glue one's eyes on all three ASI's all the way down the runway to lift-off.

In contrast, a rough idea of what the ground speed should be at say 80 knots or 100 knots ASI during the take off roll will give you a rough idea of rotate speed. Forget V1 by now, because that is IAS and things may be happening too fast for it to be meaningful, practically speaking.

Boeing allude to this when it advises "ground speed information is available from the FMC and on the instrument displays. These indications can be used as a cross check".

To keep this discussion in perspective just remember the Boeing 80 knot or AirBus 100 knot ASI check is for gross errors - not just a few knots. same with the ground speed check if used. Again as stated in the Boeing FCTM, conditions beyond control of the flight crew may preclude following a maneuver exactly. The maneuvers are not intended to replace good judgement and logic. Good logic suggests a knowledge of the expected ground speed during the mandatory ASI check on the take off roll.

[IFixPlanes]

Originally Posted by Jim Croche

Brookfield
For info, the A320 doesn't have manual lift dumping on the ground during an RTO or landing. The system uses weight on the wheel(s) to give partial or full lift dump. This, in turn, triggers the autobrake to work. If not enough weight on wheels, no spoilers therefore no lift dump and no autobrake and pulling the speedbrake lever will not extend them!! What a lousy system and it's been implicated in numerous accidents and incidents (Garuda, TAM for example).

Hi Jim, first make yourself sure what happened at TAM accident.
The aircraft sensed WOW but with one trottle not at (or near) idle you have no ground spoilers actuation and therefore no autobrake.

[safetypee]

A37575 Re: You should not make the mistake of confusing airmanship with company SOP.
Agreed; I could have chosen better wording, perhaps ‘airmanship and stewardship’ (organisational management – safety management) to represent the joint individual and organisational responsibilities in risk assessment – perhaps tactical and strategic assessments respectively.

I do not like, or wish to encourage the concept that company SOP is primarily designed to cover litigation, even if true.
IMHO this encourages pilots to relinquish their responsibility for safety, restricts thinking, and might lead to reduced flexibility which is essential for both safety and profitable operation. Furthermore if operational management think this way, then they too might stop looking at safety because they feel that their responsibilities are covered – safety is good enough, the SOPs meet the rules, and if not followed – blame the pilot. This is a slippery slope.

I agree with your discussion on the problems of identifying a speed error (failure is easier to detect) and the aspects of training. However, it should be the tenor of training to improve skill in crosschecking airspeed in these situations – knowing where to look, what to compare, and why, which appear to be the primary issues not understood by many newer / inexperienced pilots. (Experience isn’t about time on type; it’s about knowing what to do, when, and why to do it).

Perhaps the Boeing ‘FMC’ cross check was introduced after an instrument related accident. Thus, by introducing a new check (if only as guidance – or as legal cover), the reaction, to an accident which should have been prevented by other means, has unwittingly added confusion (complexity) which is open to misuse / misinterpretation.

[CONF iture]

Space pig, Lederhosen was not mentioning the autobrake system but the automatic speed brakes (spoilers) deflection logic ...

[Kerosene Kraut]

CVR is said to be useless as it was not stopped and got written over.

[Denti]

Any source for that? The CVR usually stops with both engines cut off in the 737, however you can restart it manually. Recording time is of course 2 hours as the aircraft was only a few months old.

[Kerosene Kraut]

Source? Just rumours as this is a rumours forum.