RTO on a field limited takeoff-where do I end up?

[Blue system]

Hi.

Question to the performance wizards.....

Rejecting a takeoff at V1 on a wet runway....in theory where do
I end? The the takeoff i field limited.
Will I have the main wheels on the runway end or the nosegear?

Regards,

[PIK3141]

Assuming Field Length limited, at the correctly computed limiting weight, and at the V1 for a wet runway for that weight, then you should be stopped at the Balanced Field Length Distance, which should be short of the runway or stopway end. Not to be so would be in contravention of the JAR / FAR regulations which build in a time delay for recognition and reaction of maybe a couple of seconds.

[mutt]

What type of aircraft, where was it certified and what year was it certified?

Mutt

[Blue system]

Atr 72 and B-737.
Where it was certified and what year I dont know but I could find out.
Maybe you now anyway?

Regards,

[galaxy flyer]

The model of B-737 also has a bearing on the answer, me thinks.

If you recognized the problem calling for a reject AT V1, you might well end up in the grass. The first action to begin the reject is required to happen BY V1, not the recognition of the problem.

GF

[A-3TWENTY]

Theoretically you stop in the runway , in practice...probably in the grass.

Specially in a heavy

According to airbus if you reject at V1+4kts , you will cross the oposite threshold at 65 Kts.

A320

[Old Smokey]

There's a number of 'it depends' in this topic, interestingly the 2 aircraft chosen (ATR-72 and B737) are one of them. Mutt has asked after the year of certification, and that's another one of them.

Assuming that you have strictly completed the recognition and reaction within the times used for certification, and assuming that both aircraft are being operated in their 'Native' region (Europe and the U.S.A), the following applies......

The ATR-72 will stop with it's nose-wheel at the end of the ASDA.

The B737 will stop at the ASDA plus the line-up allowance (because FAR 25 does not require consideration of line-up allowance, whereas the JAR does).

If the B737 is being operated and registered in a region (such as Australia) where the line-up allowance must be considered, then it's stop performance will be as per the ATR-72.

The era of certification is important. In ye olden days, Accelerate-Stop performance was based upon engine failure, with continued acceleration with OEI until implementing 'Stop' procedures (This would be so for an old B737-100 and -200). In the modern era, acceleration between recognition and implementation of 'Stop' procedures is based upon all engines. Thus, a modern era aircraft will stop with it's nose-wheel at the end of the ASDA (or ASDA + Line-up in the U.S.A), whilst an older certified aircraft would perform similarly in the event of a reject due to engine failure, but over-run the ASDA for an 'All Engines' stop.

There are a number of 'It all depends' scenarios in this topic, these are a few of them.

Best Regards,

Old Smokey

[aerobat77]

when i am right the stop distance is calculated without the use of reverse , so when you abort for something other than an engine failure and the reversers work you should be ok.

[FE Hoppy]

and sometimes when you're wrong :-)
May be included as an additional means of deceleration using recommended reverse thrust procedures when determining the accelerate-stop distance on a wet runway, provided the requirements of sub-paragraph (e) of this paragraph are met. (See AMC 25.109(f).)


It's an option these days.

[aerobat77]

ah ok, you ever learn something new !

[Blue system]

Thanks Old Smokey!

Do you know where I could find à reference for your exellent information?

Regards,

[Escape Path]

May be included as an additional means of deceleration using recommended reverse thrust procedures when determining the accelerate-stop distance on a wet runway, provided the requirements of sub-paragraph (e) of this paragraph are met. (See AMC 25.109(f).)

Is it the same for a dry runway?

[FE Hoppy]

Nope, but this question was specifically for wet.

[Flaps90]

Isn't the ASDR factored to 1.3? So you "should" end up nowhere near the end.

[Max Angle]

It most certainly is NOT factored, there is no margin.

[Flaps90]

I believe that if your performance graphs do not have you applying a safety factor then they are already incorporated. Being FL limited by ASDR (not if your performance is based on balanced field because you will be TODA limited) and rejecting at V1 will not put you at the end of the stopway.

[Blue system]

There is à built in margin at certification of 2 seconds. This time is given to allow for "the normal line pilot" transition versus test pilot transition. If you are
quicker than certification standards them you will stop before rwy end and vice versa.

Regards,

[FE Hoppy]

The AFM expansion is a distance equal to 2 seconds at V1. There are also minimum times for each of the actions (up to 4) required to stop the aircraft but there is no 1.3% correction. The head/tailwind 50/150% may have an effect as long as there is some.

In the end if you are rejecting on a wet runway at V1 you will end up there or there abouts depending more than anything on the actual braking coefficient which is assumed in the case of wet runways and if you're skating on 10 years of rubber and grease you might be lucky to stay out of the garden!

[Old Smokey]

Flaps90,

Your Quote - I believe that if your performance graphs do not have you applying a safety factor then they are already incorporated. This is not the case for a Wet Runway Takeoff, which is the subject of this thread. In this case ALL of the reserves have been used up. In the case for the Dry Runway, Reverse Thrust is (typically) not considered, being kept as a 'Reserve' means of stopping (I say 'Reserve', as the manufacturer may keep one other means of stopping in reserve, as is required by legislation).

Blue system,

The reference for the information is written into the regulations themselves, FAR, JAR, CAO etc. If these are read, you will find references to, for example, "Aircraft certified before 1966" etc. There is no ICAO standard (unfortunately), thus the individual legislations of each state must be studied.

Best Regards,

Old Smokey

[framer]

I am by no means an expert on this subject but have a boeing document that has some basic figures that may be helpful to this discussion.
I'l cherry-pick some statements;
"The manner in which the additional 2 seconds of time in the RTO trasition segment has been accounted for has changed over time. Prior to 1981 one second was added to the second and third pilot actions (throttle cut and spoiler extensionrespectively), during which time the aircraft decelerated."
There was an ammendment (25-42) where the distance became 2 seconds at continued acceleration. Then there was another ammendment (25-92) where the 2 seconds is calculated at V1 speed, to my knowledge this is the current state of affairs (I'm happy to be corrected).

"The distance associated with this 2 seconds time for the 737-800, 777-200, and 747-400 is approximately 500-600 feet"

The requirement to factor the wind by 50% or 150% (head or tail) also provides a 'factoring element'.
A 737-800 at MAUW and 30 degrees celcius using idle reverse 2 engines should give you 160ft extra, detent reverse 290ft extra, and max reverse 300ft extra runway. That is of course for a dry runway and I realise the question was about a wet runway.
Like I said, I am no expert, these are things I have gleaned from one document and I look forward t the input from the likes of old smokey.
Framer

[Old Smokey]

framer,

Everything that you say is true:ok:

No further comment is necessary, excepting that you've brought up one more 'it depends' to add to the list. Recognition, reaction, and putting Stopping action into effect times are just one more thing that has changed over the years. (It's also the reason that I cautiously say Recognition and Reaction times in posts rather than quoting the number of seconds, it varys).

Without second guessing Mutt, this is again one more reason for his asking from which era the aircraft was certified.

Regards,

Old Smokey

[mutt]

The original question asked where an aircraft would end up following an RTO at V1 at a Runway Limited Weight on a wet runway. I would say that for older pre 1981 aircraft such as the B707,B727,B737-100/200, B747-100/200/300/SP, DC-8, DC-9, DC-10, MD-80, certified under FAR25, they are guaranteed to end up completely off the end of the runway in the dirt, even on a dry runway. There are a number of reasons for this:


[1] Certification requirements, Vef was assumed to occur 1 second prior to V1, then the brakes, throttles and speed brakes were applied allowing for a total of 3 seconds prior to the aircraft transitioning into complete stopping configuration. There was no allowance for residual thrust nor additional acceleration during the transition.
[2] Available performance software during that era, be it Mark7 or Topaz or Tops, they didn’t allow for a line up distance, so whatever runway length was lost during the line-up would push the stopping point off the runway by a similar amount.
[3] The aircraft brakes used during certification were new steel brakes, with new tires.
[4] The WET calculation was based on reducing the V1 by 15kts and the RWY LWT by 10% as at that time there was not wasn’t any other basis.


Post 1981, things started to change with the use of flight test timings for transition of brakes/throttles/speed brakes followed by a 2 second buffer at Vb speed. There was also a great improvement in the available software such as accounting for line-up distances. This would have applied to the B757,B767, B747-400, B737-300/400/500.

In 1995 with the certification of the B777-200/300, MD11 and MD90, they started to apply “Amendment 42”, this allowed 2 seconds at continued acceleration followed by timings for flight test transition of brakes/throttles/speed brakes. The use of worn brakes was introduced as well as the first digital aircraft flight manual chapter 4 for the B777. This method required the longest stopping distance. Boeing also started to introduce operations manual data based on FAA AC91-6A/B, this accounted for specific Mu factors associated with different runway contaminants.

In 1998, the certification of the B737-NG, B757-300, B767-400 and B717 introduced Amendment 92, this allowed for 2 seconds constant speed at V1, followed by timings for flight test transition of brakes/throttle/ speed brakes. This was also the first time that WET runway data was incorporated into an FAA AFM.

That’s the FAA history, I presume that there is an equivalent for UK CAA or DGAC regulations.

We conducted tests in a Level D Full Flight B747-300 simulator using the appropriate software to train crews to get used to high speed RTO’s, we were never able to get the simulator stopped on the runway even with the use of thrust reversers, we queried the simulator manufacturer and Boeing about this, the answer from both was that it “should” stop on the runway as per certification. We conducted the same test with B772 and B744 FFS with carbon brakes, they stopped easily within the runway length.

So you see that there is no easy specific answer, it all depends on where your aircraft was certified, and when!

Mutt

[hvogt]

The B737 will stop at the ASDA plus the line-up allowance (because FAR 25 does not require consideration of line-up allowance, whereas the JAR does).Interesting, Old Smokey. I didn't know that. Nevertheless, if you operate under EU-OPS you have to take the line-up distance into account (EU-OPS 1.490 (c) 6).

[Old Smokey]

Absolutely true hvogt, within the 'operating state' (Europe in this case) the local requirements apply for operations, i.e. the B737 must consider line-up allowance if operated under EU-OPS.

In the B737's 'Native State' (USA), the local rules apply, and an RTO would end up off the end of the runway under limiting conditions.

Just one more 'It Depends'..............

Best Regards,

Old Smokey