V1 question

[BGQ]

With respect FlightSafety, the question didn't allow the abort at V1-10. The poor candidate gets to answer on the basis of two not so great options.... continuing at V1-10 or stopping at V1+10.

Normal training would have us do the opposite. I suspect the interviewer was trying to see how well the candidate understood the implications of both.

He could have added further complication by suggesting the takeoff was a reduced thrust takeoff on a wet runway where V1 is already reduced by 10kts... so you would be going at V1-20 or stopping on a wet runway at V1+10.

Bet nobody wants me interviewing them for their next job now !

[Old Smokey]

I think that Flight Safety got it right, it's a weed-out question at interview. I was curious why Mutt and John_Tullamarine didn't take a bight at this one, they typically would, but methinks that they saw what Flight Safety saw. Of course, Mr. Gullible (ME) was "In like Flynn". I should have stuck to my original post in this thread (#7) where I said that neither option was acceptable. Such is life.

oldebloke, from one oldie to another, I don't have an aversion to Wet runway data at all, in fact it's essential. What does concern me significantly is the criteria used in determining the data. I've done a lot of flight testing, including RTOs at limiting conditions, and to put it lightly, they're a close run thing. Statictically the RTO produces a far greater number of accidents and serious incidents than does the continued Takeoff case. It's not just a statistical thing, there are very generous performance margins provided for the continued Takeoff case, but precious little for the RTO, and therein lies the root cause of the statistics. The only bonus is that, for dry runways, we have no accounting for reverse thrust. Many pilots place great stock in this, all the roaring and snorting of full reverse seems impressive, but in terms of Accelerate-Stop distance reduction, the bonus is very small, but nevertheless a bonus. The certification for the wet runway consumes in it's entirety the only bonus that we ordinarily have (reverse thrust), leaving us NOTHING. As for the 15 ft screen height, NO, I don't think that it is nearly enough. I know that the 35 ft screen height is simply an arbitrary 'line in the sand' (as John_Tullamarine would put it), but not too bad a 'line in the sand' at that. One regulatory authority to which I prepared and submitted performance data point blank refused to accept the 15 ft data (although legal) insisting upon 35 ft on all occasions. It was the happiest refusal of my career, I relished the additional work to re-do the performance data for 35 ft, with the Regulatory Authority to hold up to the company as the 'bad guys', not me.

What really bugs me is when the F/O pulls out the wet runway data for a runway that could only be described as a bit damp. Good manners prevail, but I'm sorely tempted to say "What? You want to take away the only margin that I have?"

Just my thoughts, and as for the Singapore wet runway situation, I would say that we have less wet runway "time' here than elsewhere. It comes down in buckets, makes our runways very wet for an hour or so, and goes away. In some places it just rains aaaallll day

Rant over,

Regards,

Old Smokey

[fireflybob]

Would not another factor be the topography of where you are?

I would not want to go off the end at, say, Madeira or Luton (RW 26), where there are "vertical drops" down to the beach or Vauxhalls factory (if it's still there!) but a few feet low at the screen height would not worry me quite to much!

Alternatively some runways have stacks of "emergency distance" beyond the end of the "official" ASDA.

[Jonty]

This developed some discussion on a recent trip to Dalaman.
We decided that the question was nuts as either course of action will result in disaster.
But having said that we reckon that its better to stop at V1+10kts than go at V1-10kts. The reason being that in either case your going off the end of the runway, but if your stopping at V1+10 then at least your slowing down. If your going at V1-10 then your going off the end of the runway with full power and no breaking effect.

[Obscurum per obscurius]

Chaps, RTFQ. The question says FAILURE at V1 +/- 10kts, not action. Since the mid 90s V1 has been redefined, it is no longer a failure speed or a decision speed it is an action speed. Simple!
"The maximum speed in the takeoff at which the pilot must TAKE THE FIRST ACTION to stop the airplane within the accelerate/stop distance.”
Thus any failure must occur some time before V1 for you to safely decide and then take action prior to or at V1.
Of interest the B777 'ENG FAIL' alert on the PFD is inhibited 6 knots before V1, I think those clever chaps at Boeing are trying to tell us something!

[Jonty]

Originally Posted by Obscurum per obscurius

Since the mid 90s V1 has been redefined, it is no longer a failure speed or a decision speed it is an action speed. Simple!
"The maximum speed in the takeoff at which the pilot must TAKE THE FIRST ACTION to stop the airplane within the accelerate/stop distance.”

It also states: "V1 also means the minimum speed in the takeoff, following the failure of an engine at which point the pilot can continue the takeoff and achieve the required hight above the takeoff surface within the takeoff distance"

Also when the AFM is produced all the figures are predicated on a failure 1 second before V1

So to answer the question you need to know the acceleration rate of the aircraft. Which is why its a naff question!

[Obscurum per obscurius]

If the AFM calculations are "predicated on a failure 1 second before V1", then surely that equates to roughly 5-10kts.

I know I wouldn't be able to make the decision AND first action within 10 kts of a rapidly approaching V1.

So the safest option has to be to continue if you have a failure just below V1.

[AirRabbit]

Originally Posted by tornadoflyer

I would very much appreciate it, if any forum member could provide some inputs to the following question:
What would be more dangerous? Engine failure at V1-10 knots and continue or engine failure at V1+10 knots and abort.
Thank you in advance.

This is sorta like the question "What do you do before you land?" Well, there isn't just one answer, and it greatly depends on what assumptions you make as you decide what answer to give.
When I was doing some interesting work with a -10 series DC-9 about a hundred years ago, we made several takeoffs "on one engine." It takes a good deal of nosewheel steering input along with judicial application of the single engine's thrust until the rudder gets aerodynamically effective, but the takeoffs were no problem. Of course we were at the old Clinton-Sherman Air Force Base in Oklahoma, with almost 13,000 feet of concrete and the airplane was at relatively light weight. So, under those circumstances, experiencing an engine failure at V1-10 knots and continuing the takeoff would be no sweat. And, I would suspect that an abort at V1+10 knots wouldn't have been a real sweat either. Now start taking large chunks of runway away from you, jack up the gross weight, and the sweat begins to become more prevalent - all the way down to a balanced field for the conditions. In that scenerio (i.e., balanced field) I'd go with the old addage that its better to stop when you can't stop than to go when you can't go. Of course, I'm sure you could come up with conditions that would turn that upside down as well!
Sorry, I know that doesn't answer your question very well, but that's the nature of such questions. Oh, and by the way, the answer to "What do you do before you land?" -- The answer I gave was "takeoff."

[DOVES]

Thank you AirRabbit!
Now I know! Now I've seen the the light!
Why should I study (after 40 years, 20.000 flying hrs, 4 carriers, 12 type ratings etc.) those silly things (almost a 7000 questions test: I'm becoming a VFR I.P. to honorably and altruistically complete my career) like VMCG, VMCA, Second segment, obstacle limit, Low energy and High energy rejected Take off, and the reasons why we perform them, etc.; when/if YOU tell us that it's possible to take off with a single engine on a twin! (Do you remember a brand new B-747/400 trying to take off from Hong Kong on three, and miserably ending in the lagoon?)
Please Fly Safe
DOVES

[A330AV8R]

Did you say 10 kts after V1 and ABORT T/O ????

[DOVES]

And now my opinion:
It's better to continue T.O. with a failure 10 kts before V1; with some 'distinguo' in case the failure is an engine one: What's our weight today? is our a balanced T.O.? which the meteo condintions and the rwy contamination? Is the field elevation high? Are there obstacle in the T.O. path?.
Never abort T.O. (10) any single kt(s) after V1 for any reason! (Except of course in case of a locked elevator)
Fly SAFE
DOVE

[AirRabbit]

Originally Posted by DOVES

Thank you AirRabbit!
Now I know! Now I've seen the the light! Why should I study (after 40 years, 20.000 flying hrs, 4 carriers, 12 type ratings etc.) those silly things (almost a 7000 questions test: I'm becoming a VFR I.P. to honorably and altruistically complete my career) like VMCG, VMCA, Second segment, obstacle limit, Low energy and High energy rejected Take off, and the reasons why we perform them, etc.; when/if YOU tell us that it's possible to take off with a single engine on a twin! (Do you remember a brand new B-747/400 trying to take off from Hong Kong on three, and miserably ending in the lagoon?) Please Fly Safe DOVES

Excuse me? Well, Doves, when (or if) you get your blood pressure back down below the price of gold (for just a moment) and dial down the sarcasm (just a bit), I'd like to suggest that you go back and re-read what I posted. After doing so, you'll likely see that I was NOT advocating anything close to disregarding aircraft performance. As someone with your experience should know, IF you have enough runway in front of you (as I obviously did in the example I provided) the question asked (should you or can you stop 10 knots past V1 speed; or should you or can you continue if you lose an engine at V1 speed -10 knots) is almost IRRELEVANT! THAT, my very experienced (40 years, 20.000 flying hrs, 4 carriers, 12 type ratings etc.) friend, is what I was pointing out. I sincerely hope that you aren't spring-loaded to such a sarcastic self-serving monologue EVERY time you quickly read something and reach an erroneous conclusion. Remember, sometimes it is wiser to keep one's mouth closed and risk looking like a fool, rather than opening it for confirmation.

[SAM 2M]

UK CAA AIC

See AIC 141/1998 Pink

Rejected Take Off - UK Registered Aircraft

[DOVES]

Dear AirRabbit
Perhaps I didn't understand exactly what YOU meant. YOU will pardon me my less than perfect mastery of your language; and that's one of the reasons why I won't sink in a sterile bickering in answering (without opening the mouth) your last aphorism.
YOU wrote:
..."When I was doing some interesting work with a -10 series DC-9 about a hundred years ago, we made several takeoffs "on one engine." It takes a good deal of nosewheel steering input along with judicial application of the single engine's thrust until the rudder gets aerodynamically effective, but the takeoffs were no problem. Of course we were at the old Clinton-Sherman Air Force Base in Oklahoma, with almost 13,000 feet of concrete and the airplane was at relatively light weight. So, under those circumstances, experiencing an engine failure at V1-10 knots and continuing the takeoff would be no sweat. And, I would suspect that an abort at V1+10 knots wouldn't have been a real sweat either."...
Am I right?
1) I would only have justified YOU if YOU were in a simulator. I confess that I was taught the same manoevre in the sim. during my last type rating in the 737-300, almost 4 years ago; the Instructor told us: "Who knows? Some day you could face an emergency situation in which this could be the only escape route". I would even have admired YOU if YOU were doing some test flight, alone on board.
2) ..."So, under those circumstances, experiencing an engine failure at V1-10 knots and continuing the takeoff would be no sweat."...
But YOU forgot to mention which engine failure: the one kept idle 'cause I'm sure YOU would never had taken off with one engine shut down on a twin'; or the other at full thrust; in which case continuing the takeoff to the rotation would have been very very very difficult.
I've always thought that the art of flying is very far from the circus. Fly the numbers, as OLD SMOKEY writes often, and I add: Fly the books.
Perhaps that's the reason why I'm still flying airplanes and not a 6-Drawer Oak Desk.
Fly Safe
DOVE

[earnest]

Can I recommend everyone follows SAM 2M’s lead and reads the relevant AIC. The AIC Sam quotes has recently been superseded by AIC 24/2006, by the way. This document finally lays it all out in, I think, simple and unambiguous terms, and hopefully will lay these arguments to rest, at least in the UK.

http://www.ais.org.uk/aes/pubs/aip/pdf/aic/4P094.PDF (You need to register but it’s free).

A few quotes from the AIC:

2.1 The decision speed (V1) is the highest speed by which the pilot should have made the mental decision to reject the take-off in the event of a relevant failure. Safety margins, in the form of delay times or extra distance on either side of V1, are built into the accelerated-stop distances published in performance data issued in compliance with JAR-OPS 1 and the Air Navigation (General) Regulations.

2.1.1 Thus, considerations of pilot recognition of a failure and reaction in response to that recognition are allowed for.However, V1must be respected as the latest speed by which a decision to stop must have been taken to assure a stopping capability within the distance available on a limiting runway.

2.2 The published accelerated-stop distance makes no allowance for a decision to stop from beyond V1. It follows, therefore, that such a late decision presumes a judgement that a failure, or combination of failures, has occurred such that getting airborne would pose a greater risk than overrunning the end of the runway. On anything close to a limiting runway, the overrun is liable to occur with the aeroplane still travelling at significant speed and to impose a significant risk to the aeroplane and its occupants.

2.3 Some margins are provided in the continued take-off performance in the event of a decision to continue the take-off with an engine failure below V1 but these could be eroded to such an extent that the aeroplane may not be able to lift off by the end of the runway and/or to clear obstacles once airborne. This is particularly so when using a 'wet' V1.

[airamerica]

''Which is better: failure 10 kts before V1 and continue T.O or failure 10 kts after V1 and abort T.O?'’

Simple isn’t it or am I missing something??????

If a reputable company asks this type of question, well ask your self the question why are you being asked this question?

‘’This hypothetical V1 question is being asked by a reputable company to prospective candidates’’.

Two key words to be considered here.

‘’Reputable’’ –how was that status achieved? And the second word-‘’prospective’’- obviously not by hiring ‘’prospective’’ pilots who tend to question the sciences associated behind the rules, especially by pilot extraordinaire’s that perhaps know something that years of testing yielded unfounded results.

Answers are all about justification for following laid down prescribed rules, procedures and regulations, and from a ‘’prospective’’ point of view- hence you are tested on your decision making skills with an own explanation as to why you would choose either.

What a pointless debate.

Oh and safe flying.

[AirRabbit]

Originally Posted by DOVES

Dear AirRabbit
Perhaps I didn't understand exactly what YOU meant. YOU will pardon me my less than perfect mastery of your language; and that's one of the reasons why I won't sink in a sterile bickering in answering (without opening the mouth) your last aphorism.
YOU wrote:
..."When I was doing some interesting work with a -10 series DC-9 about a hundred years ago, we made several takeoffs "on one engine." It takes a good deal of nosewheel steering input along with judicial application of the single engine's thrust until the rudder gets aerodynamically effective, but the takeoffs were no problem. Of course we were at the old Clinton-Sherman Air Force Base in Oklahoma, with almost 13,000 feet of concrete and the airplane was at relatively light weight. So, under those circumstances, experiencing an engine failure at V1-10 knots and continuing the takeoff would be no sweat. And, I would suspect that an abort at V1+10 knots wouldn't have been a real sweat either."...
Am I right?

It appears that the “quote” function works correctly, if that is what you are asking.

Originally Posted by DOVES

1) I would only have justified YOU if YOU were in a simulator. I confess that I was taught the same manoevre in the sim. during my last type rating in the 737-300, almost 4 years ago; the Instructor told us: "Who knows? Some day you could face an emergency situation in which this could be the only escape route". I would even have admired YOU if YOU were doing some test flight, alone on board.

Perhaps its because English is not your native language, but I’m not sure what you mean about you “justifying ME if I were in a simulator.” Let me be clear. I was in an airplane, not a simulator. In fact, I WAS doing a flight test. As you probably would recognize, it would be foolish and irresponsible (not to mention illegal) to operate a DC-9 alone. Therefore, we had several folks on board – as you might understand, you typically have a couple of other folks along when doing flight tests.

Originally Posted by DOVES

2) ..."So, under those circumstances, experiencing an engine failure at V1-10 knots and continuing the takeoff would be no sweat."...
But YOU forgot to mention which engine failure: the one kept idle 'cause I'm sure YOU would never had taken off with one engine shut down on a twin'; or the other at full thrust; in which case continuing the takeoff to the rotation would have been very very very difficult.

Well, let me correct my oversight … no, we did not make the takeoffs with one engine shut down. The takeoff tests were done from as close to the approach end of the runway as we could maneuver the airplane, and with brake release, slowly added thrust on one engine until we reached the computed maximum takeoff thrust for that engine. And, yes, it was somewhat difficult. As I mentioned, it took considerable amount of nose wheel steering and forward control column pressure to maintain adequate directional control until the rudder became effective. And full thrust on the one engine was not possible until adequate airflow over the rudder allowed it. But once that occurred, full thrust on the one engine wasn’t much of a problem; and yes, we did continue the takeoff roll through the rotation, and getting airborne. And, each pilot on board did it several times, alternating the engine used, ultimately achieving full thrust on one engine for each takeoff. In each case the other engine was running at forward idle thrust. Pilots made takeoffs from both the right and left seat.
The reason for my example and the point I was making – but apparently not sufficiently well for your understanding – was that if a pilot were to experience an engine failure at V1 –10 knots and have a substantial amount of runway still in front of the airplane, OR to accelerate to a point of V1 +10 knots and experience a serious problem at that point with the same substantial amount of runway still in front of the airplane, the question of whether the takeoff should be continued or the takeoff should be rejected is almost irrelevant. The irrelevancy coming from the fact that there would still be enough runway in front of the airplane to support a continued takeoff or a rejected takeoff decision.

Originally Posted by DOVES

I've always thought that the art of flying is very far from the circus. Fly the numbers, as OLD SMOKEY writes often, and I add: Fly the books.
Perhaps that's the reason why I'm still flying airplanes and not a 6-Drawer Oak Desk. Fly Safe DOVE

Well, there we agree – flying is no circus – and I happen to agree with OLD SMOKEY about flying the numbers. Personally, however, I prefer to fly the airplane not the book. I don’t know very many “books” that have made a good decision or landed any airplane. And, with all due respect sir, if you manage to continue to fly safely for a long enough period, maybe your company will promote you too, and let you do your flight briefings and debriefings at a similar 6-Drawer Oak Desk. They kinda “grow” on you.