V1

[CowlFlapsOpen]

Thanks. Interesting idea. Could be fun actually.

[CODY614]

Test pilot time......

Jeff T.

[CowlFlapsOpen]

Indeed, rev to full throttle, roll, cut, and brake like mad! Gonna work on it today. The more I thought about this I realized that if V1 is defined
as the speed at which it is possible to come to a stop on the remaining runway it could exceed VR on really long runways. Thus its upper bound must be
VR (by definition).

Jeff

[Leftcoaster]

'From the Ground Up' a Transport Canada approved basic aviation primer, offers the following definitions for V1, Vr and V2. Text in
quotation marks is verbatum.

V1 - "critical engine failure speed. Take-off decision speed. The speed above which the take-off is continued , and below which the take-
off is abandoned in the event of an engine failure".

Vr - "rotation speed."

V2 - "take-off safety speed. Take-off and climb speed."

I have seen slightly differing definitions in U.S. and European or perhaps more detailed explanations elsewhere but the above are a good
place to start. I use Vlof ("lift-off speed') for taildraggers instead of Vr. Be advised though, that I'm not a real world pilot, just a flight
simulator enthusiast.
Cheers

[CODY614]

CowlFlapsOpen wrote:
Indeed, rev to full throttle, roll, cut, and brake like mad! Gonna work on it today. The more I thought about this I realized that if V1 is defined
as the speed at which it is possible to come to a stop on the remaining runway it could exceed VR on really long runways. Thus its upper bound must be
VR (by definition).

Jeff

Doh!
Isnt' that what we(Me and Silo) tried to beat into you 15 replies ago?
Gawd this stuff is addicting......You made me read some manuals today!.....

[KenG]

Cowlflaps,

In the case of most light twins these aircraft are not certified with a V1 or a V2 speed. FARs Part 23.51, 23.67, 25.107 and 25.121 explains
how aircraft are certified and how the manufacture is to determine these speeds. While V1 is determined by the manufacture with specific runway
performance in mind, it is not dependent on the length of the runway. That is V1 for a 2,000 foot runway is the same as for a 13,000 foot runway. Just
on the prior you may not have accelerate-stop distance. That being said there is no real way to compute a V1 for an aircraft that does not have one.
(again this is done by manufactures.) While LeftCoaster gives a technique for determining a V1 speed this is based on accelerate-stop distance only
and a distance that is based on a selected length of runway. This does not take into consideration accelerate-go distance and accelerate-go over a 50'
obstacle. These are all tests that a manufacture must perform with highly qualified test pilots.

The best bet is to try and find real world V1, VR and V2 speed and hope that the person who did the aircraft dynamics modeling got it right. In the
past I have worked with various modelers on aircraft performance on various King Airs. This is not an easy task as you fix one thing, cruise speed and
a given altitude and it will throw off acceleration time performance during the take-off roll. While pilots do have a good number of charts available
to us we often do not have all of the charts used during certification. It is always a compromise.

If you absolutely cannot find any good Vspeed numbers then you might have to try various methods of computing a set of numbers. I would always
recommend that you start with ISA condition from an airport at sea level. There are a couple of scenery files that are designed for testing aircraft
performance with runway distance markers. The first set of Vspeeds I try to find are VS0 and VS1 as I can then interpolate some numbers from them such
as VREF and VR. On a large airplane with multiple flap position I will find the stall speed for each position. This goes into a chart. I then repeat
the test at the same weight at ISA+30 and again at ISA-30 and record the numbers again. I then follow these tests up with VMCA testing again at ISA,
ISA+30, and ISA-30. (You can go into the aircraft config file and look up the stall speeds these should match your ISA flaps up and flaps full down
speeds.) I perform these tests as close to the ground as I can. 400' AGL is optimal. (No I would never try this for real at 400'.) Ok I now have my
stall speed at various flap configurations. By multiplying them by 1.3 I can compute the VREF. If the VREF speed is below VMCA+3 then VMCA +3 is my
VREF speed. I also have a basis for starting to compute a VR speed. For VR I start with 1.1 X the stall speed in take-off configuration. For V2 I can
compute a V2 speed is 1.2 times the stall speed in the takeoff condition. Again all speeds should be above VMCA. I then test to see if under ISA
conditions at 400' and with one engine failed I can achieve the following climb gradients: 2.4% for twins, 2.7% for three holers, and 3.0% for four or
more engines. If the airplane can not perform to these standards at ISA and MTOW then I would not perform engine out in this aircraft.

Whew, we now have a bunch of VR, V2 and VREF speeds through charting straight line between the numbers for ISA -30, ISA and ISA +30 we can
extrapolate number for temperatures in between. Performing the stall tests at 5,400' and 10,400' I can also extrapolate the difference for altitudes
between SL and 10,000'. Finally I would test at minimum fuel and load and a loading right in the middle of minimum and MTOW at each temperature and
altitude and finally I have a set for numbers from ISA -30 to ISA +30 from SL to 10,000' that can be used.

However I have not touched V1. This is because V1 is a decision speed and based on engine failure on VEF. VEF is determined by the manufacture in the
certification process. So here is where some flying policy comes into play. Airlines who operate heavy equipment have come to realize the danger
associated with high speed aborts, in such they recommend continuing the take-off in most cases where speed is equal to 10% below VR, unless such
take-off with put the passengers at greater risk (fire or big parts coming off the airplane.) Thus for V1 you would be safe making it 10% less than
VR. Now with those speeds we can start to makes some distance measuring first with accelerate-stop tests at each temperature and weight (and airports
close to the altitudes, Denver International and Lake County are close.) Then followed by accelerate-go tests. If you reach an altitude, temperature,
or weight in which the aircraft lumbers and will not takeoff then you have found the maximum performance of the airplane and you should not attempt
take-offs under those conditions.

[Dutch64]

Good to see there is a lot of knowledge on this forum. Whatever thread, i didn't see any question left unanswered so far, Great!

[CowlFlapsOpen]

Thank you Ken for the great answer. This was what I was looking for and makes sense. After I posted I continued to look at some reference books and
was begining to come to the conclusion that V1/V2 were not germane for the twins and singles I fly. (FAA's Airplane Flying Handbook had a nice
discussion, but it was in the Jet section--perhaps that should have been a clue.) This of course is consistent with their absence in the Perfomance
specs sections of the POHs for these ac. I can usually find VMCA and of course VSO and VS1 from the cfgs or POH. I can the extrapolate. I also had
decided that I would use a another rule of thumb for decision speed--VR by half the runway length. I started paying a little more attention to how
far I had travelled down the runway, etc. Anyway thanks again. By the way, can I ask where you instruct? Looking for a good school for this spring.

[KenG]

Your Welcome.

I fly state aircraft and I instruct for the Government.

There are many good schools out there, I always recommend a Part 141 school as they are inspected by the FAA and always have a course syllabus. This
also depends on what your final goal for tickets are. Some student pilots who have lots of MSFS experience have found that they receive more focused
training by attending a course at their local FBO.

Personally I attended initial training taking Aviation Science at Northwestern. I then received specialized training by the Government and follow-on
and recurrent training at Flight Safety Intl. I received my International training through CAE Simuflite.

[CowlFlapsOpen]

Thanks. Still shopping for a Part 141. Looking into a school out of Northeast Philly (took an intro flight there a few days ago and was really
impressed) , but a job-related move to the west may complicate matters. Don't think I should start and then switch schools. My local FBO has no
schools, only individual CFIs who are available. After the look into Philly, I started to realize that I probably wanted a flight school not just
indivivual instruction. The school had space for ground school, several instructors, about a dozen acfts including both high and low wing trainers,
and a few simulators for those overcast days.

[detpilot]

Check out Western Michigan University. If you come get a tour, I'll likely be your guide. http://www.wmich.edu/aviation

[CowlFlapsOpen]

Thanks Detpilot. Just got back to this thread. Sorry for the slow response. Not out of the question actually. Used to reside in Ann Arbor and may
have occasion to return to that part of the country.