View Full Version : Accelerate stop distance required
Dariuszw
10th Jan 2012, 08:13
My Cessna Citation charts provide me with V1 speed but nowhere can I find accelerate stop distance required. Is takeoff distance required computed as ASDR ? I think not since it provides me with distance to screen hight of 35feet. Why would Cessna omit ASDR charts ? As a pilot I would like to know not only my V1 but ASDR esspecially on short runways. And since they came up with V1 it must be based on some required accelerate stop distance....right ? Or am I just confused.....Any help would be greatly appreciated.
Why would Cessna omit ASDR charts - because you do not need them! You have no real way of judging how many ft/mtrs you have left at the time the engine goes bang so what use are they to you? V1 is all you need and Cessna worry about the rest.
Now can you tell us - pilot or simmer?
Johnny F@rt Pants
10th Jan 2012, 10:24
BOAC - I can think of one good reason somebody might wish to know their ASDR.........
If you know your ASDR then you know whether the stop end RVR needs to be accounted for when taking off in LVP's:ok:
Darius - don't know I'm afraid, however apart from what I have written above, BOAC is quite correct, there's no other good reason that I can think of to know your ASDR.
DBate
10th Jan 2012, 10:24
Now can you tell us - pilot or simmer?
Have a look at his profile... Age: 16. I guess the question is answered. ;)
Dariuszw
10th Jan 2012, 14:22
BOAC - V1 should ensure that I can accelerte to decision speed then stop within ASDA which is the worst case scenario. So Cessna must assume certain safe distance exists if I can accelerate to lets say 100kts and then be able to stop within runway environment. As a pilot am I to believe blindly that if I decide at 100kts to stop on a 4000ft runway everything will be ok ...and how about 3000ft or 2000ft long runway ....still V1 at 100kts ? Thats insane ! My charts only consider weight and field elevation with no runway consideration whatssoever. I need to know how much distance I will need to stop at V1 !
Is there someone who knows aswer to this question ?
Darius please let us know what you are before we spend time on this.
Denti
10th Jan 2012, 18:00
It is SSG...
Yes - we tried this before,but 'he' claimed not to be 16. Suggest we ignore?
galaxy flyer
10th Jan 2012, 21:01
Your Cessna charts must give a field length for the weight, pressure altitude and temp. That is balanced and as long as you have begun the first action to stop OR have continued the take-off, you will be stopped at that distance or 35' in the air. Cessna, like other business jet operators, does not provide all the charts because no one wants to pay for them, nor do most corporate operators want to do the performance engineering.
BOAC, now I returned and saw your post--QUITE AGREE.
M-ONGO
10th Jan 2012, 21:16
Oh no, not again!
http://www.pprune.org/questions/472366-v1-light-plane.html
http://www.pprune.org/tech-log/472470-question-regarding-fuel-consumption-higher-altitude.html#post6919010
Dariuszw
11th Jan 2012, 03:45
gallaxy flyer - for a long time that was my assumption as well that Cessna providing required takeoff distance includes ASDR in its computation but recently came to conclusion that this is not so. Assume you accelerate to Vr which happens to be V1 as well and then you decide to aboard. There is no way in this world you will convince me that distance it takes to climb just 35 feet from that rotation point is the same as stopping fully loaded plane from such high speed. It takes me perhaps (Im guessing) 3 seconds to climb to 35 feet. So you try to convince me I will stop in approximately the same time ? No way my friend !
It takes me perhaps (Im guessing) 3 seconds to climb to 35 feet. So you are telling us that you usually conduct single engine takeoff from V1 in the actual aircraft....... interesting :{:{:{:{
Just to make sure that we are on the same wavelength, would you like to explain to us what BALANCED FIELD means?
If you dont believe us, why dont you contact Cessna directly, give them your tailnumber and have them explain the concept to you, or Flight Safety, CAE etc.
Mutt
M-ONGO
11th Jan 2012, 07:23
Troll
Assume you accelerate to Vr which happens to be V1 as well and then you decide to aboard.
A professional pilot would not abort at V1 - the decision is already made to continue at this speed.
Assuming you did abort at or after V1' the handling performance of the aircraft would depend upon whether it's modelled upon Microsoft FS or X-Plane. Maybe get yourself a set of USB rudder pedals to help keep straight?
Dariuszw
11th Jan 2012, 08:52
I have tried somewhere else to post this question to no avail so will repost here hoping that someone can help me aswer it. For a long time my assumption was that Cessna Citation providing required takeoff distance includes ASDR in its computations but recently came to conclusion that this is not so. Lets assume I accelerate to Vr which happens to be V1 as well and then decide to aboard. There is no way that distance it takes to climb just 35 feet (screen height used for takeoff distance computation) from that rotation point is the same as stopping fully loaded plane from such high speed. It takes me perhaps (Im guessing) 3 seconds to climb to 35 feet. So how can I stop in approximately the same time ? So when takeoff charts tell me I need 3000ft takeoff distance it is based on performance to 35feet and can not include any computation for V1. For takeoff computation all I need is pressure and temp. and runway length does not even come into consideration. So what assurance do I have when aboart at V1/Vr point I will have enough distance to stop. Any help would be greatly appreciated !
http://www.pprune.org/questions/473831-accelerate-stop-distance-required.html
FLEXPWR
11th Jan 2012, 10:55
Am I reading from the wrong website? :eek:
Or is this PSRuNe?
It seems that for all these years I have "faithfully" used V1, but some new genius in aeronautics is getting all my beargins wrong! :E
Dariuszw
12th Jan 2012, 04:18
After some research I have found the answer. Just as I expected actual takeoff distance to 35feet screen height would not have allowed safe stopping distance in case aboart was initiated at decision speed/rotation speed. What Cessna has done is to combine three different computations:
accelerate-stop distance
accelerate go with single engine to 35ft distance
and two engine takeoff distance multiplied by 115%
Longest distance of the three of those cases was given as takeoff distance.
Unfortunatly Cessna does not explain that by takeoff distance tables assuming correctly that most will follow blindly never considering that actual takeoff distance would never allow to stop in case of V1/Vr cut.
Hope someone will find this usefull !
Dariuszw
12th Jan 2012, 04:27
After some research I have found the answer. Just as I expected actual takeoff distance to 35feet screen height would not have allowed safe stopping distance in case aboart was initiated at decision speed/rotation speed. What Cessna has done is to combine three different computations:
accelerate-stop distance
accelerate go with single engine to 35ft distance
and two engine takeoff distance multiplied by 115%
Longest distance of the three of those cases was given as takeoff distance.
Unfortunatly Cessna does not explain that by takeoff distance tables assuming correctly that most will follow blindly never considering that actual takeoff distance would never allow to stop in case of V1/Vr cut.
Hope someone will find this usefull !
I'm lazy so Im just going to report Brian Abrahams reply to the same statement from Darisuzm in the Tech Forum....
Quote:
Unfortunatly Cessna does not explain that by takeoff distance tables assuming correctly that most will follow blindly never considering that actual takeoff distance would never allow to stop in case of V1/Vr cut.
Rubbish, not that the sentence makes any sense. The CJ2 is certified to FAR23 and amendments 1 through 40, plus selected provisions through to amendment 51. The FAA also imposed Special Conditions (as you fly the aircraft you tell us what they are). However landing, take off, climb and one engine inoperative criteria are all FAR25.
Quote:
Hope someone will find this usefull
Not in the slightest.
Thanks Brian :ok::ok::ok:
Brian Abraham
12th Jan 2012, 12:07
Unfortunatly Cessna does not explain that by takeoff distance tables assuming correctly that most will follow blindly never considering that actual takeoff distance would never allow to stop in case of V1/Vr cut.You'll need to explain that analysis. I suggest it's rubbish. Only have CJ3 & 4, and they are both the same format, so it would surprise me if the 2 were any different.
http://i101.photobucket.com/albums/m56/babraham227/z054.jpghttp://i101.photobucket.com/albums/m56/babraham227/z053.jpg
On both the 3 & 4 V1 never equals Vr, and I'll bet the 2 doesn't either.
I'd say you have little understanding of what the charts are saying, and proves once and for all that you don't fly a Citation - if anything.
Hope someone will find this usefullNope, not in the slightest.
Wizofoz
12th Jan 2012, 12:25
There are many more Citation models than just the CJ2,3 and 4 you know!!
galaxy flyer
12th Jan 2012, 13:55
Well, 2,500 hours in the original C I and C II, they have split V1 and Vr speeds, too. Fraser was PM, Carter was President and bell bottoms were leaving the scene.
While Cessna's explanation leads to the assumption that accel-stop and accel-go maybe different distances, they are almost certainly "balanced", hence the split between V1 and Vr. To the OP, remember, in the GO case, at V1 the take-off was continued on ONE engine, rotated and climbed on that ONE engine. In the STOP case, the first action to stop was taken by V1 and maximum braking applied until stopping. Easily the same distance, as I have seen once or twice. So few pilots ever use max braking that they do not believe how fast speed goes away.
Dariuszw
12th Jan 2012, 14:21
How much you want to bet Brian and you galaxy-flyer that Cessna does have V1 and Vr equal?
Im always open for bets and better yet since you fly CJ3 I have those charts with me as well and will post those charts proving to be correct. Go ahead put your money where your mouth is and bet with me 100$ right now !
I will give you guys few hours to accept the bet and then will post charts anyway just for fun of embarrassing you and your 2500h of apparently wasted time. :\
galaxy flyer
12th Jan 2012, 14:57
Loads of planes have dry conditions where V1 = Vr, the B727 and Global Express come to mind in my experience. Doesn't change the fact that a balanced field, one where the stop and go distances are equal, is what is charted because a balanced field is the SHORTEST possible distance. Any other selected V1 will result in one of the two distances being longer than the other.
Why would the manufacturer, with legal liability, fail to either use the balanced field or present the required charts for computing unbalanced fields? BTW, I have great familiarity with the manufacturer's side of this problem.
Suffice to say, those field lengths given will allow either a stop or go, if you follow the conditions that went into producing them.
Dariuszw
12th Jan 2012, 14:59
mutt, Darius just made an offer for a 100$ bet with your friends on tech forum. Suggest to observe it to see if they'r stupid enough to accept it. I have no doubt they are but not that stupid to actualy accept it. Either way this 16 year old will teach them and morons like you a lesson.:)