V1, whats your take?

pimper · Post by **pimper** » Wed Mar 09, 2005 9:38 pm

Due to the increase in engine failures/rejected takeoffs lately at SG, I have been discussing what V1 means while at work.

Assuming a balanced field what does V1 mean to everyone in here?

flyincanuck · Post by **flyincanuck** » Wed Mar 09, 2005 9:45 pm

A decision HAS TO BE MADE AND INITIATED PRIOR TO V1.

It's commonly mistaken that that V1 is a 'decision speed'...it's not. The decision has to be made prior to V1 call out.

If you think about it...V1 is the maximum speed at which you may safely stop the aircraft. Well if you call V1, think about aborting, and then initiate it..you're looking at an additional 2, 3, 4 (or more) seconds. That's defeating the purpose of V1.

'Plane' and simple.

peeelot · Post by **peeelot** » Wed Mar 09, 2005 9:46 pm

It is the speed where the SG md83 engine fails

Duster · Post by **Duster** » Wed Mar 09, 2005 10:06 pm

Fire or engine fail prior to V1 - Reject
After V1 go flying. The only caveat to this would be if there was some other major fault that would lead one to believe the bird wont fly - e.g. jammed or restricted controls

mental vomit · Post by **mental vomit** » Wed Mar 09, 2005 10:58 pm

pimper wrote:Due to the increase in engine failures/rejected takeoffs lately at SG, I have been discussing what V1 means while at work.

Assuming a balanced field what does V1 mean to everyone in here?

Don't they teach you this shite before you haul your first pieces of meat, wee man?

Panama Jack · Post by **Panama Jack** » Thu Mar 10, 2005 1:59 am

V1 is the decision speed. The thing is that YOU don't make the decision, but the decision has been made for you. At V1, you are going flying.

On the PPRUNE forum, heard someone define "happiness" as "V1 at Lagos, Nigeria."

pimper · Post by **pimper** » Thu Mar 10, 2005 4:39 am

Flying Canuck I agree with you 100%. V1 is the speed at which the first action of the reject has to be initiated to stop the plane on the available runway/stopway. So what is the point of calling V1 at V1 like most carriers do?

I think there is a large misconception that a reject can be accomplished if the failure is prior to V1 but the reject actions are not initiated till slightly after V1.

V1CUT · Post by **V1CUT** » Thu Mar 10, 2005 5:05 am

V1 determines the speed which you should continue the takeoff or reject with remaining runway, "90kts normal" "90kts reject"

hence V1CUT

V

Bleed Air · Post by **Bleed Air** » Thu Mar 10, 2005 5:40 am

Heres one for you
So your flying your ac light off a really long runway.
So your actual V1 is now equal to your Vr because it can't be higher, and you have an eng failure at V1 with 8000 ft infront of you, still go flying???

TopperHarley · Post by **TopperHarley** » Thu Mar 10, 2005 6:08 am

Here's how TC defines it (for commutters):

"The takeoff decision speed, V1, is the calibrated airspeed on the ground at which, as a result of engine failure or other reasons, the pilot is assumed to have made a decision to continue or discontinue the takeoff. The takeoff decision speed, V1, must be selected by the applicant but must not be less than VEF plus the speed gained with the critical engine inoperative during the time interval between the instant at which the critical engine is failed and the instant at which the pilot recognizes and reacts to the engine failure, as indicated by the pilot's application of the first retarding means during the accelerate-stop determination of 523.55."

An easier way to think of V1 is as follows- V1 is the speed where it must be possible to abort the t/o and bring the a/c to a complete stop, based on the current conditions, on the runway plus stopway, OR, continue and be at V2 at 35 feet above the departure end of the runway/clearway. This comes from the ATP Aerocourse Book.

Panama Jack · Post by **Panama Jack** » Thu Mar 10, 2005 6:16 am

Bleed Air wrote:Heres one for you
So your flying your ac light off a really long runway.
So your actual V1 is now equal to your Vr because it can't be higher, and you have an eng failure at V1 with 8000 ft infront of you, still go flying???

Unless you feel that your aircraft has suffered some sort of catastrophic failure that prevents it from flying (an engine failure is not a catastrophic failure), the answer is "yes."

Bede · Post by **Bede** » Thu Mar 10, 2005 6:17 am

V1 is usually the decision speed. Technically it is the speed at which the distance to stop equals distance to continue to Vr and be 50' at V2. I knew a guy who flew a 320 and lost an engine at V1-10. He was on a short strip (6000') and decided to continue. He figured at his weight he would have blown the tires, gone off the runway and ended up in a ball of flames. He continued and everything turned out fine.

Ray Darr · Post by **Ray Darr** » Thu Mar 10, 2005 6:32 am

Panama Jack wrote:...someone define "happiness" as "V1 at Lagos, Nigeria."

PJ, technically that should be "V1 + a 'C-Hair'". Oh and if you have to ask...ahem...never-mind.

TTJJ · Post by **TTJJ** » Thu Mar 10, 2005 7:08 am

Panama Jack is correct. V1 is a GO speed. Many more accidents have been caused by rejecting than by continuing the take off.

Airlines have been teaching for quite a while to call V1 5kts before the actual V1. This gives the pilot the time to see a failure and initiate a reject before V1. With this he should stay on the runway.

Bleed Air wrote "So your flying your ac light off a really long runway.
So your actual V1 is now equal to your Vr because it can't be higher, and you have an eng failure at V1 with 8000 ft infront of you, still go flying???"
If you are flying a light twin you would stop. That is the reason you leave your gear down until there is no usable runway left."

On a transport aircraft you are trained to continue for one reason. A number that has been beat into your head for 20 years (V1) has been reached. At this critical/stressful time of an engine failure, they want your training to take over and not have the pilot trying to second guess or determine if he/she can still stop the aircraft. A DC-10, in Jacarta I beleive, tried to do just that and ran off the end of the runway destroying the A/C.

Bede Wrote" I knew a guy who flew a 320 and lost an engine at V1-10. He was on a short strip (6000') and decided to continue. He figured at his weight he would have blown the tires, gone off the runway and ended up in a ball of flames. He continued and everything turned out fine."

Continuing before V1 is a crap shoot. It might work but you will definately be eating into your 35' over the other end.

I have to agree with the A-320 driver's thinking though. I've seen dozens of times where the F/O calls V1 and I think "not a hope in hell this thing would stop in time."

Sim. training on V1 always gives the following:
V1 reject - note runway remaining
V1 go - note height over end of runway

V1 minus 10 - go - note loss of height over end of runway and additional runway required
V1 plus 10 - reject - note distance stopped past end of runway
V1 plus 10- go - this is for the WTF delayed rotation factor.

Airplains were made to fly. They are pretty awkward creatures on the ground. If in doubt, fly the thing even though your mind is screaming to stay on the ground. (Unless you are below VMCA of course)

It all boils down to training.

V1 is not a decision speed. The decision must have been made already.

V1 is a GO SPEED

TopperHarley · Post by **TopperHarley** » Thu Mar 10, 2005 7:21 am

Bede,

Isnt that definition you provided the definition of "balanced field length," and not V1?

Panama Jack · Post by **Panama Jack** » Thu Mar 10, 2005 7:29 am

PJ, technically that should be "V1 + a 'C-Hair'". Oh and if you have to ask...ahem...never-mind.

Is it? I am under the impression that V1 (the exact speed) is the speed to continue. I know most airlines have adopted this philosphy now.

Ray Darr · Post by **Ray Darr** » Thu Mar 10, 2005 8:08 am

Time to hit a liming spot, grab a frosty few, then re-read my reply. Tongue in cheek. Any SLIGHT chance to remain in Lagos is a bad thing, ergo, the further away from there the better...ergo V1 + ANYthing would lead you away (hopefully!).

A thousand smax to Panama Jack, please, moderators. He hasn't gotten out lately.

Panama Jack · Post by **Panama Jack** » Thu Mar 10, 2005 8:44 am

Ray Darr wrote:A thousand smax to Panama Jack, please, moderators. He hasn't gotten out lately.

Ooooh, how right you are. hiding

Cool Rythms! · Post by **Cool Rythms!** » Thu Mar 10, 2005 9:39 am

True, the decision to abort must not be made at V1, but prior. It's all about reaction time brothers and sisters. Think about it for a second. You experience an engine failure, or some sort of emergency on the roll. There will be a delay in the time it takes for your brain to process the data and tell you whats actually happened, a delay in making the decision to abort, a delay in closing the thrust levers and having the engines spool down, a delay in jumping on the brakes and of course with all or most jets (assuming your flying a jet that is), a delay between the time you pull up the thrust reverse levers and the time they fully deploy. Any guesses as to how far past V1 you've accelerated at this point if you decided to abort at V1? Thats why the decision has to be made before and not at V1. Attempting to abort a take-off at or above V1 will ensure that you are going to go off the end of the runway, or at least come real close to it. And of course, we havn't even mentioned anything about contaminated runways. If an emergency occurs at V1, consider yourself already flying and react accordingly. Look what happened with that Challenger that went zooming off the runway recently. I don't want to speculate, because I don't know all the details. But it seems like an aborted take-off initiated way too late. In any case, it's an interesting topic, which I think will keep this thread going for a good while.

tripleseven · Post by **tripleseven** » Thu Mar 10, 2005 9:44 am

Bede,

On a short or slippery runway, V1 should be reduced due to the possibility of having a fan go with minimal runway left, thus preventing the ball of fire you describe. I hope your friend who flies transport category aircraft knew this, or looked up the speeds before takeoff, and didn't just guess. We should leave the eyeball method of takeoff calculations to the beaver and otter pilots.

On another note, there is another speed known as Vcef, which is the critical engine failure speed. Vcef is the highest speed which an aircraft can be accelerated, lose an engine, and then continue the takeoff or stop in the computed minimum field length. (Fly the Wing, p.55) The relationship between Vcef and V1 is that V1 is 1 s later than Vcef, to account for pilot reaction.

DeskDriver · Post by **DeskDriver** » Thu Mar 10, 2005 10:00 am

Forget about V1. There is a more important decision moment affecting operations which occurs after taxing to parking.

Assuming the pilots are on a day long layover, if they arrive at the bar at 1500 hours and their next flight is the subsequent day at 1900 hours. V8 represents the decision made at 2230 when the bar runs out of Clamato juice and yet the crew want a double Caeser

Jaques Strappe · Post by **Jaques Strappe** » Thu Mar 10, 2005 10:04 am

Didn't you guys learn this in school? Everyone knows the most important decision to made is where to drink beer when you finish the day.

Ray Darr · Post by **Ray Darr** » Thu Mar 10, 2005 10:32 am

Isn't the question: "If clamato mix runs out, is it ok to use a V8?"

pimper · Post by **pimper** » Thu Mar 10, 2005 1:29 pm

I might be a little rusty on perfomance but I believe if you have an engine failure after V1 on a balanced field you are only guarenteed to cross the end at 15 feet.

As for rejecting with lots of runway left, this would no longer be a balanced field meaning you might get away with..but then again you might not so I would be inclined to continue the takeoff.

So the question remains, when should you call V1. My take on it...if V1 is called right at V1 you are already to late so why not call it sooner?

Taking off on a slippery runway and reducing your V1 when you are field limited is also another can of worms.

Benwa · Post by **Benwa** » Thu Mar 10, 2005 1:35 pm

I think it's quite simple, if something goes wrong before you hear V1: REJECT.

If you notice something going wrong and then hear V1, go on with take off.

V1 is not a call to check things up. It just means it's too late to stop.

V1, whats your take?

V1, whats your take?

Re: V1, whats your take?

V8?