View Full Version : High Speed Aborts
max2105
18th Oct 2002, 13:36
Have been asked to give a presentation as to importance of V1!
Would love to hear any stories of high speed aborts and subsequent investigations!
PaperTiger
18th Oct 2002, 18:10
http://www.bst.gc.ca/en/reports/air/1995/a95h0015/a95h0015.asp
Section 1.14 is what interests you I think.
Dan Kelly
19th Oct 2002, 02:11
About 3 or 4 years ago I saw a short video on High Speed Aborts. I'm pretty sure it was produced by Boeing. Perhaps they could help if you've enough lead time.
Boeing produced a Takeoff Safety Guide in conjunction with the FAA. The guide comes complete with a video and would help you produce an excellent presentation.
Contact you local Boeing rep for a copy, or try myboeingfleet.com if you have access. (Checked out MBF, the presentation is available for download, 14 meg.)
Good Luck.
Mutt.
A-V-8R
19th Oct 2002, 13:40
Please check the accident incident reports in the US for a story about a DC-8 at Orlando, Florida in the early 90's
I witnessed it. Apparently the FAA was giving a Type Rating ride in a DC-8, I think the straight pipe engine one, not the CFMs.
I heard the 8 tell the Orlando tower that "This is a rating ride with the FAA, and we will be doing a practice abort on the runway.
They did indeed. Blew out half of the tires and cause a small fire....
ECAM Status
19th Oct 2002, 19:54
As far as I know Airbus has also produced an interesting video when it comes to the importance of abandoning t-off at or below V1. It was very interesting to watch and the reason it was being produced , was to make pilots to be go minded above 100 kts (i.e. even below V1). It was by no means produced to abolish the term V1, but just to make pilots think twice for abondoning t-offs above 100 kts. It will be very interesting if you have the opportunity to watch this video.
Those that have been involved in heavy jet airline flying for a long time are usually inclined to be GO minded. A high energy stop is not nice...for anyone.
lomapaseo
20th Oct 2002, 03:59
>Those that have been involved in heavy jet airline flying for a long time are usually inclined to be GO minded. A high energy stop is not nice...for anyone.<
You bet, 5 out of 100 result in very bad consequences (like off runway events)
Lou Scannon
27th Oct 2002, 11:18
I can still remember the immediate comment by a Spanish Captain who had just aborted take-off when above V1, having experienced severe and unexplained airframe vibration.
He said that he didn't know if his action had unnecessarily killed a small number of passengers or miraculously saved the lives of nearly everyone on board.
When the cause was finally established it turned out to be a nose tyre failure.
I really felt sympathy for that man as it is always obvious what a pilot should have done, long after the event.
lomapaseo
27th Oct 2002, 19:16
Interesting data in the link above, however yet another piece of data in a large database shows that 5% of the aborts above 100 kts (without relation to V1) result in major incidents during the abort. This might suggest pilot technique in the causal link rather than just too fast to stop.
It would be difficult for me to examine the incident data above V1 simply because most incidents don't accurately report actual decision speed vs V1 (almost invariably they report the incident *at* or near V1 (but rarely do they report it as *above*).
I suspect that most of the Boeing data supporting the 2% rate they speak of is limited to corroborated data using DFDR recorders.
It's interesting to note that 78% of runway over-runs after an RTO were with 10 KTS below V1.
Very interesting high speed abort occured with a Continental DC10 off 06R in LAX years ago....the Captain (on his last flight before age 60) aborted at V1+? ....due to a shredded tire. Asked later what he would have done differently, his reply was..."call in sick".
True story.
OTOH, spoke with an old GulfAir Captain long ago who stated emphatically that he would never take an aeroplane with an engine fire into the air, no matter what the speed.
Needless to say, he did not get along with his First Officers all that well...:rolleyes:
lomapaseo
28th Oct 2002, 10:25
> OTOH, spoke with an old GulfAir Captain long ago who stated emphatically that he would never take an aeroplane with an engine fire into the air, no matter what the speed. <
That's the main reason for automatically disabling the engine fire annunciator on takeoff above certain speeds. Far better to fly the aircraft first and then deal with an engine fire.
In-flight engine fires are rarely catastrophic in the air once the fuel has been shut-off. Most of the bad experience has been pool fires under the wing after the plane has come to a stop.
Max Angle
28th Oct 2002, 13:35
One of the interesting points about V1 go/no-go situations is that there is NO margin built in to the figures. The climb performance in the various stages of the take-off after an engine failure has a small margin built into it (ie Net performance) which means it is very unlikely that you will not meet the stated performance. There are no such margins in the V1 stop/go part of the equation, you are dealing with gross performance and there is a very real chance that in a runway limiting situation you can do everything right and still end up off the runway.
The prospect of a over run on an limiting runway prompts some people to consider continuing the take-off even if they are slightly below V1. This also has huge risks depending on your location. On a take-off that is not field limited there is a spread of possible V1 speeds that fall between the min. and max. V1. The Max V1 is a speed after which you cannot stop in the remaining lenght, the min V1 is a speed below which there is not enough runway left to accelerate on one engine to VR and get airbourne. One figure is used to keep things simple but on a field limited take-off at max. weight the figures are the same and if you continue the take-off after an engine failure more than a few knots below V1 you are unlikely to be able to achieve VR by the end of the tarmac.
On balance of course it is far better to be go minded but the other side of equation is well worth bearing in mind I think.
There are no such margins in the V1 stop/go part of the equation,
What about the "reaction times", the use of Thrust reversers and accounting for worn brakes, arent these margins?
Mutt
lomapaseo
29th Oct 2002, 00:50
>here are no such margins in the V1 stop/go part of the equation,
What about the "reaction times", the use of Thrust reversers and accounting for worn brakes, arent these margins?
Mutt<
Trouble is that if you attempt to count reaction times as margin for success, just as many times it will be a margin against success given that it also increases pilot error rate in doing the wrong thing by a quick reaction. "trained reflex" is more like what is needed but, to accomodate all pilots the training needs to consider typical reaction times.
The same kind of argument can be made about reversers. Seeing as how many aborts involve yaw and or perceieved engine failure, you start to get problems with the pilot grabbing a handful of throttles and than trying to dither the correct ones to aid in activating just the right combinations of reverse thrust. This is relatively easy when you have lots of time (landing) but might not be the first thing you are going to do in the first 5 seconds of a high speed stop with yaw.
Your mileage may vary, so I'll await and see if anybody has actual experience with this on the forum. All mine has been negative:)
Captain Stable
29th Oct 2002, 08:06
Allowances for reaction times, brakes not being as efficient as they might etc. are all built-in to the published V1 tables/procedures. It's all part of factoring the performance data.
NorthernSID
30th Oct 2002, 12:31
Daft question, I know, but.....
I work in the military FJ community and sit in the back doing the thinking, EW and radar etc.
we use V go, V stop, V rotate, V unstick V embs etc for Go-safely airborne 1 engine, stop with/without using cables, rotate & unstick are obvious and embs = emergency braking speed at which you can stop the ac using brakes only in remaining runway. All are individual runwayaand temperature specific.
I've never related these to equivalent civilian V1, V2 etc, so what are they exactly? - or if not QFI exactly, aircrew practical may be more use!!
I have high speed aborted, but have the advantage of rev thrust, a cable, usually a barrier or eventually martin baker so my experiences may be a little different!
Captain Stable
30th Oct 2002, 23:09
These are simplified, so I hope people will bear with me:-
V.1 = speed beyond which it is not possible given the length, slope and condition of runway available, temperature, pressure altitude and weight of aircraft to stop without running off the end. It actually has two definitions, and I won't go into the other, which is more performance- and structure-related, but this is the worst-case scenario. Beyond this speed, even with an engine failure, you are going to take it into the air and then sort it out.
V.R = Rotate speed. Obvious, really. Dictated by the manufacturers, based mainly upon weight, temperature, pressure altitude and flap settings. V.R always>=V.1.
V.2 = Speed to be held crossing a 35 foot screen at the end of the runway. Generally considered to be take-off safety speed. Basically, with gear down and take-off flap, you can stay in the air at this speed and still have an engine failure.
Lots of other speeds called different things by different manufacturers and different operators, but these are the most important ones.
Hope that answers your question.
NorthernSID
31st Oct 2002, 11:48
many thanks, clearer now
GlueBall
4th Nov 2002, 18:46
To preclude any second guessing after V1, our SOP has the Captain's hand come off the throttles by V1. Once the captain's hand has been removed from the throttles, our company rule of law is: "Don't even think about aborting the takeoff roll."
When the F/O makes the takeoff, the captain's hand is on the throttles, because only the captain makes the decision to abort prior to V1.