Sxmarbury33 From United States of America, joined Oct 2000, 445 posts, RR: 0 Posted (10 years 1 month 1 week 5 days 23 hours ago) and read 2953 times:
This question is inspired by the other thread on V1. Ill give a senario, a lightly loaded 712 is taking off from a runway with 11k+ feet of runway at close to sea level on a standard temp and pres day. There has to be a V1 from what im told and when this happens the V1 is the same as VR (correct me if im wrong). but lets say the 717 does not de rate takes off in 5000ft meaning the pilot has 6000+ ft of runway left for an abort. Techniclly the plane can handle the problem in the air if it isnt one of the doomsday senarios but since every malfuntion varies with degree wouldnt it be safer to have a real stop go V number the pilot to utlilize?
B747Skipper From , joined Dec 1969, posts, RR: Reply 1, posted (10 years 1 month 1 week 5 days 23 hours ago) and read 2928 times:
Could you rephrase your question...
P.S. - What is a 712...
I am just a pilot, I think I know what you are asking.
But could you clarify, I will try to help, with pleasure.
Happy contrails -
Sxmarbury33 From United States of America, joined Oct 2000, 445 posts, RR: 0 Reply 3, posted (10 years 1 month 1 week 5 days 22 hours ago) and read 2899 times:
yea sorry i meant 717-200. But i just mean a plane lightly loaded where a 11K runway is overkill meant mainly for long haul flights ie jfk's 13R which im assuming at times handles smaller short haul aircraft.
B747Skipper From , joined Dec 1969, posts, RR: Reply 4, posted (10 years 1 month 1 week 5 days 21 hours ago) and read 2881 times:
I do not know your aviation knowledge background, so I use simple words to explain. Hope you do not mind that I use the 747-200, as I am more familiar with that aircraft than the 717... and give you speeds that make sense.
Suppose I am at JFK, 150 passengers only, and the airline tells me to stop in MIA, to take another 200 passengers bound for EZE. I will probably be given runway 31L, because of the LH turn on departure and heading South.
My plane is obviously very light, few passengers, enough fuel to make MIA + reserves, as you said, the 15,000 feet-long runway is an "overkill"... Say my weight is only 500,000 lbs. My speed V1 would be 120... I could do with a short 7,000 feet long runway (half the length of that runway length available).
Despite the fact that I have tremendous "excess of concrete" in front of me, if an engine failed at say, 125 knots... I would continue the takeoff, because that is THE procedure... Yet I know, that 15,000 feet long runway could accommodate a takeoff at 833,000 lbs, which would have a V1 speed of 170 knots. I could abort for an engine failure at 165, and still "stop the plane"...
Even though it is strange to you maybe, yet, standardization and procedures require me to take my decision go/no-go at 120 knots, for my takeoff with the light airplane going to MIA... That is what "the book" says...
Is that sufficient explanation...?
Happy contrails -
AAR90 From United States of America, joined Jan 2000, 3437 posts, RR: 49 Reply 5, posted (10 years 1 month 1 week 5 days 21 hours ago) and read 2861 times:
Sounds like my Hawkeye days... takeoff in 800 feet with 11,200 feet of runway remaining.
... but since every malfuntion varies with degree wouldnt it be safer to have a real stop go V number the pilot to utlilize?
However, what good is a "real stop" speed if I'm already flying?
You did say: ...and when this happens the V1 is the same as VR...
Once I've begun rotation I'm in a flying configuration and all accellerate/stop calculations no longer apply. OTOH, (I think I know what you're thinking) I can always use my "emergency authority" and perform an emergency landing in the available runway in front of me --that's the way USN lawyers explained the legal language to me once.
*NO CARRIER* -- A Naval Aviator's worst nightmare!
Chdmcmanus From United States of America, joined Mar 2001, 374 posts, RR: 2 Reply 6, posted (10 years 1 month 1 week 5 days 16 hours ago) and read 2782 times:
Essentially the situation you have given illustrates the use of balanced field ops due to the excessive runway. However, the procedures approved for the given carrier do not give the option of reverting to the old "go speed" concept, and the approved procedures must be followed. Basically the TOLD will extend V1 to meet Vr and the operator will follow their given procedure. I agree with both B747Skipper and AAR90 completely. I also know exactly what you are talking about, just two weeks ago I departed from PAEI (Eielson AFB, AK) with 14507 ft of runway and a 352,000 lb DC-10-30F (KC-10). The USAF requires the FE to manually compute all TOLD prior to takeoff (I know, the dark ages but that's the way we do it), and even with the full balanced field and 5 flaps, our CFL was about 6500ft, leaving 8007 ft remaining. Using the V1 concept, we were required to use normal procedures, and had a catastrophic emergency occurred we would have performed as such, even though from a physics standpoint our "commit speed" was at least 30 knots higher than rotate, once the acft is "wing supported" all bets are off for stopping, thus our published procedures are the safest to follow. It just means that you use a full derate, min flaps, and climb like a homesick angel, blowing through V2, Pressure height for acceleration, Vfr and Vsr as fast as you can grab the handles! What a great departure! IMHO, the most useless things to an aviator is Runway behind you, Altitude above you, Fuel on the ground, the book you didn't read, and the procedure you didn't practice, and this covers three of them at once.
Keep the paint side up and the rubber side down!
Mandala499 From Indonesia, joined Aug 2001, 6426 posts, RR: 74 Reply 7, posted (10 years 1 month 1 week 5 days 3 hours ago) and read 2669 times:
If you 717 can go to V1 and stop again within the runway permitted, and say another 6000ft excess, once you've passed V1, with the engines blaring... how many feet will you use up while you idle the engines?
Unless there's a counter in the panel saying "xxx kts xxxxft available abort OK/Not OK" display... I wouldn't do it! Such a thing don't exist anyways.
In some airline (not aircraft) manuals I've read, Aborting past V1 is only permitted "if in your professional judgement, the airplane will not be able to continue flight and would only cause greater damage/casualty by continuing the flight." It went further... "There are no reliable calculations available to determine the outcome of a post V1 abort. Hence it is the airline's policy for the flight to continue should a problem occur past V1, unless the forementioned circumstances prevail."
Even jet aircraft manuals say the residual kinetic energy passing 80 knots would make an abort difficult.
2 examples of Post V1 abort.
The only "reasonable" but still debated post V1 abort I know is the Garuda DC10 crash at Fukuoka... The plane rotated and the crew found the airplane cannot go beyond V2, with the aircraft about to enter a stall, the PIC aborted the flight to keep the crash within airport perimeter and not the surrounding urban area. Some reports mentioned the engine #2 was beginning to fail and high vibrations occured on engine #3. It was also found the aircraft was possibly overweight due to a despatch/loadsheet error/foulplay. Dark days of Garuda.
An unreasonable post V1 abort... Lion Air's 732 PK-LID early 2002. Pekanbaru was 2200m runway. The aircraft was light, aircraft commenced take off roll and rotated. Upon rotation, the aircraft would not fly above 10ft, while still accelerating. The PNF realised that Flap1 was selected but not indicated. Fearing stall and an INOP stick shaker, PF panicked and called abort. The aircraft was "dropped" onto the runway and lost stability due to asymetrical thrust during spooldown, veered off runway into trees. No casualties somehow. Aircraft was written off. Right gear ripped, right engine ripped, wing spar broken. The NTSC (Indonesia's NTSB) found that the aircraft should have deployed flaps even after rotation to to augment lift as the aircraft was light and was still accelerating when the abort came.
Conclusion, follow the published procedure... unless you know you'll die continuing or aborting (professional judgement not withstanding).
My useless 2 cents contribution...
When losing situational awareness, pray Cumulus Granitus isn't nearby !
Jetguy From , joined Dec 1969, posts, RR: Reply 9, posted (10 years 1 month 1 week 4 days 21 hours ago) and read 2596 times:
Dual engine failure is about the only logical reason that I could think of, and if that were to happen there is no decision to make - the airplane isn't going to fly any way. Granted, we could all come up with "what if scenarios" where it would be better to try and stop than continue; but they would be so outlandish as to be totally unrealistic. Are there things which can cause dual engine failures? Of course, look at the post in "Civil Aviation" about the Lear 24 that took a couple of birds this morning. You will never be able to achieve 100% safety in any activity - especially aviation. Bottom line is at V1, things are happening so fast you need to be concentrating on following established procedures rather than trying to find excuses to stop. The record has proven time and time again, you are safer in the air with almost any conceivable problem than you would be attemping a high-speed abort.
AJ From Australia, joined Nov 1999, 2380 posts, RR: 26 Reply 10, posted (10 years 1 month 1 week 4 days 20 hours ago) and read 2584 times:
The loss of the Concorde in Paris got us all thinking about V1 and it's importance. Potentially an abort after V1 would have bent Concorde, but MAY have caused fewer fatalities.
That said I fully agree with Jetguy, the time taken to absorb information and act on it does not allow for an ummm, ahhh type decision, it's V1.....go! There are infinite variables and the industry has decided that for most circumstances wrapping one's aircraft around lighting gantries etc is more risky than flying over them and attempting to return to land.
Mandala499 From Indonesia, joined Aug 2001, 6426 posts, RR: 74 Reply 11, posted (10 years 1 month 1 week 4 days 15 hours ago) and read 2527 times:
Agree with Jetguy...
It's grossly unfair if investigations say pilots are to blame because he/she did not abort past V1... Any ideas or findings that they should have aborted are made with hindsight. In the actual event, it's very very hard to determine whether you should abort or not past V1... that's why the published procedure is to continue. The wording for the allowance of post V1 abort is made with great care... priority is always to continue! Statistically... "it's a safer bet"...
The 2 examples I gave I think describes why in most cases it's very hard to decide correctly whether to abort or not post V1...
"I follow Roads"
When losing situational awareness, pray Cumulus Granitus isn't nearby !
Sllevin From United States of America, joined Jan 2002, 3376 posts, RR: 6 Reply 12, posted (10 years 1 month 1 week 4 days 13 hours ago) and read 2520 times:
I think another point to make is how V1 is determined.
It's done by test pilots, who start the takeoff roll with a specific abort speed in mind. So they are watching the ASI, and when they hit that speed, the crew directly starts the RTO procedure. testing is typically done at places like EDW, which has an excellent runway, condition-wise.
That's simply not going to happen in the real world. There's going to be a master alarm gong going off, a scanning of the instruments, and all of that adds seconds to an aircraft devouring runway and accelerating. If the alarms went off at V1, you'd be lucky to start the RTO within 500' and 15 knots of V1 speed.
And don't forget energy increases with speed. So starting that RTO 15% faster than the published speed will almost certainly ensure that you need more than 15% more runway than those test pilots used.
Training always stresses that the RTO at V1 is the most dangerous procedure you'll ever perform as a crew. Unless you think you're in more danger lifting off (a fairly well known example was an AA DC-10 with a slats-not-deployed alarm, which would have stalled in the bird), you should go fly the airplane at V1 and beyond.
Unless it's a 'killer' item, the plane WILL fly off that runway engine-out at V1. And it's a lot easier to match those numbers (because you are already accelerating, etc) than the RTO numbers.
LZ-TLT From Germany, joined Apr 2001, 431 posts, RR: 0 Reply 13, posted (10 years 1 month 1 week 4 days 13 hours ago) and read 2516 times:
I have one side question:
When there is plenty of runway available, the aircraft is light and there are no obstacles in the way, what about doing a takeoff at lower thrust setting and how this affects the takeoff procedures? May be a stupid question, but I've heard of some airlines implementing such "derated takeoffs" for fuel saving reasons and that at some airports, noise abatement procedures require such takeoff.
Rick767 From United Kingdom, joined Jan 2000, 2662 posts, RR: 52 Reply 14, posted (10 years 1 month 1 week 4 days 12 hours ago) and read 2522 times:
V speeds are re-calculated when reduced thrust settings are used for take-off. If required, V1 is reduced accordingly.
Even with reduced thrust settings and a reasonable load departing from LGW (10,000ft+ runway) V1 on the 737 is usually equal to Vr (same with the 757/767, even going to Florida).
Remember that under JAR-OPS the ASDR (Accelerate-Stop Distance Required), which must not exceed the ASDA (Accelerate-Stop Distance Available) is calculated as:
(A) Acceleration from standing to V1
+ (B) Continued acceleration from V1 for 2 seconds, with all engines operating
+ (C) Deceleration using maximum braking to a stop, assuming that the deceleration does not commence until the end of (B)
Count out 2 seconds in your head... it's a long time and we will not hang about that long if we are going to stop. Additionally we will use full reverse thrust on all operative engines during the stop, which will reduce the stopping distance further as it is assumed not to be used in the calculation in (C).
Nonetheless as any airline pilot will tell you, a decision to abort the take-off in the vicinity of V1 is never taken lightly.
It must be remembered though that V1 is calculated as both the latest "stop" speed and the earliest "go" speed.
If an engine failure occurs sufficiently below V1, and the take-off is continued, there may be insufficient runway remaining to complete the rotation and clear the screen height.
Those who say "5 knots below V1 I'm going regardless"... beware.
I used to love the smell of Jet-A in the morning...