V1 question

[TurboS7]

Let me try.V1 is the speed at which you can abort the takeoff and apply maximum breaking with spoilers and no reverse(two engines) and stop at the end of the runway. At V1+.00000000001 you can continue the takeoff, rotate at Vr and cross the end of the runway at 35 feet.1st segment of a takefoff is from V1 to 35 feet or gear retraction 2nd segment is from 35 feet or gear retraction to 400 feet, 3rd segment or cruise segment is from 400 feet to 1500 feet. The aircraft must be able to maintain a given climb gradient for 121 and 135 on one engine assuming standard gear and flap retraction. In the case of a propeller airplane engine feathered or auto-feathered with a maximum 5 degree bank into the good engine. That's from memory after a long flight whoa, the climb gradient I think is 2.8%.

 

[Groucho]

V1 an other stuff.

The above posters are correct when they state that V1 is not runway length dependant.

However new technology and computers have adjusted the V1 scenario somewhat. Database derived performance data used by some of the larger carriers will give various V1 data for the same runway and flap data. Improved climb situaitions, used in places like LAS and other high density altitude airports, allow for increasing V1 with minimum flap settings to allow for increased second segment climb requirements. The MD-80 can have up to a 40kt V1 split from a min V1 used in a contaminated runway condition to a very high speed long and dry runway improved climb situaition.

The FAA definition of V1 does not consider runway length as a variable factor. With the new computer driven real time performance data available V1 is a highly variable speed for any given runway length. Weight, runway condition, temperature, density altitude, slope and rated or derated power settings will all change the V1 the computer puts out.

We read it off the print out and set the bugs to it. I don't know of any pilot who can explain all the factors and formulas that go into the computer models, the performance engineering department takes care of all that for us. Of course the old way of looking at the weight and looking at the flip chart speeds always works.

I hope this confuses things further.

 

[TurboS7]

We have a policy at our airline if the numbers don't work call dispatch with all the particulars, they will run all the details through the computer and then give you the go/no go. If it is a go they will give you all the supporting data via fax.

 

[FlyinBrian]

I'd be weary of accepting a "go" decisinon from dispatch without understanding how they figured their data. They don't die in the crash, and at the hearing, "dispatch said we should go" is probably not going to hold much water.

Aeronautical Decision Making philosophy:
"When in doubt, start at the hearing and work backwards"

 

[avbug]

We just go down the runway until the airplane starts to feel light. Then we pull back. If we go far enough that we start to feel queesy or tense, we pull back the thrust levers instead. If we just flat-out go too far, then we pull back the cabin door and evacuate.

Airspeed alive! 90, and crosschecked. Vee One!

Vich one?

Vis von. Over veer.

Votcha.

Votate.

Veer up! Vos vate, avter vakeoff vist, pees.

Why V1 doesn't work in Dutch cockpits.

 

[bigsky]

Alot of good and intersesting info and I don't have much to add except that the climb gradients required for the various segments vary depending on the number of engines. I believe 2.8- 2nd segment and 1.4 for the 3rd segment is correct for 2 engine a.c. and it increases to I believe 3.2 for a 3 engine and 3.5 for a 4 engine jet.(dont quote me on those numbers as Im sitting in the pub in Reykjavik, and dont have alot of references available-- but after a couple of cold vikings Im pretty comfortable with my answer.

 

[TurboS7]

bigsky how are you enjoying the dark country, I'll be up there next week. Have one for me.

 

[bigsky]

Great place actually. pitch black until 10 am but the other scenery is great(the nordic blond babe). People are friendly and lots of night life, but very expensive. Beer is about 6 US and food is also very high. Im here for a week and enjoying it alot.

 

[TurboS7]

I fly for Miami Air and I have spent a lot of time there. I acutally love the place, especially the Blue Lagoon.The NATO base is great.

 

[profile]

At FedEx we have a performance computer in the cockpit that we use to calculate this stuff, and it keeps total control of the inputs and parameters in the cockpit (There are some other carriers using these now, includeing Southwest, all of those used ours as a template).

The V1 is calculated by first attempting to use the V1max, the highest speed you can go and still stop, except our computer deducts 3000' off the runway available length to make this calculation. If performance will not allow the use of V1max and still have 3000' remaining when we "rock to a stop", it starts backing V1 towards V1min (slowest speed you can be and still continue) to try to hold that 3000'. Eventually you reach the point where this is not possible, as you've reached V1min and there is less than the 3000' "stop margin", so then it holds that, and as you increase weight you eventually reach a balanced field. The latter is not usually a factor on the smaller stuff (727s, etc) as the runway length is such that you hit Vr before you hit V1max in the first place, so the V1 is almost always Vr limited. In the larger airplanes you will almost always have a V1/Vr split unless really light.