Do you teach Rejected TakeOff?

[AuntPeggy]

What is a proper Rejected Takeoff?
Do you teach / or did your instructor teach you / Rejected Takeoffs?
What is the best method for teaching / learning / Rejected Takeoffs?

...or at least taught the student how to do a proper rejected takeoff.
And, BTW, how many of you instructors give their students a few RTO's, and how many of the rest of you have been given that maneuver in training?

I do teach rejected takeoffs and I also teach simulated low power or high DA takeoffs.

But, I also teach to use minimum braking. Unless the end of the runway is right on top of ya, use aerodynamic braking. That alone at full-idle will do a lot. I guide students to use aerodynamic braking and slowly transition to toe brakes. And, at no point should the wheels lock or even stop turning. I'm amazed at how many students (certificated pilots as well) I see spinning the plane on one tire. Just a few times on the same spot... the result will be noticed on one of the hard landings you make.

I prefer to practice RTO's one of 3 ways.

1. do a short feild take off. At about 100 to 150 feet simulate a power failure. Be ready you will have to get the nose down in a hurry to have enough energy to flare with when you lose power at Vx.

2. On Approach at about 25 to 50 feet AGL initiate a go around side step to the side like there is another aircraft on the runway. at 100-150 feet simulate the power failure. Again be careful (take you instructor with you to demonstrate) as some aircraft may not have enough energy to turn back to the runway and flare.

3. And of course practice them from any point on a normal takeoff.

Brian
CFIIG/ASEL

Well, I'm still a student (hopefully for not much longer, since we're into checkride prep) and I've never been trained to do an RTO. I've also not seen one demonstrated.

It's frustrating, sometimes, to hear people discuss things that they think are clearly important in a PPL curriculum and then realize that I've never been introduced to the subject at all. But, when it happens, I find out everything I can on the subject and then ask my CFI for dual training.

With that in mind, what's the best procedure for an RTO in a light single?

I have to admit that I probably would have been pulling the power, too, and using brakes judiciously -- maximum braking possible while maintaining directional control on the runway. If I thought I was in danger of going off the end of the runway, I'd be pulling the mixture, turning off the mags and the master switch and switching the fuel to off, in about that order. Those are the things I can think of right now without looking it up which means that's probably what I'd do in the cockpit. What's the real recommended procedure?

Thanks!

That's a pretty fair guess, although it would probably behoove you to look it up AHEAD OF TIME and learn the proper procedure for your airplane (if it exists in writing) so that you're not "winging it" when the time comes.

Likewise...and although I did teach them to a degree when I was doing primary training, I'd teach them far more thoroughly now. And that "thoroughly" would include the student chasing down some documentation...takeoff rpm minimums, various other "howgozit" points on the takeoff, stuff like that. Not just giving an abort command, or simulating traffic or a deer on the runway.

Fly safe!

David

I think this deserves a thread of its own.

 

[Everskyward]

I was curious because I thought for sure RTOs had to be in the PTS. I found out that the are in the multiengine PTS but not in the single engine section.

 

[Pi1otguy]

What is a proper Rejected Takeoff?

IDK the "proper" procedure, but as I've only flown small ASELs so far, I just do the reduce power and brake appropriately based on conditions (dry/wet, remaining runway, etc).

Do you teach / or did your instructor teach you / Rejected Takeoffs?

Didn't teach me one as such, but did do one due to a panel on the cowl opening at liftoff. However, at <20' AGL over a 5400' runway I this was more of an aborted takeoff or even a "go and stop".

What is the best method for teaching / learning / Rejected Takeoffs?

I'll defer to others for this. I'd say it just a matter of stopping before running out of asphalt, but it probably gets weird as we increase the scale.

 

[poadeleted20]

I was curious because I thought for sure RTOs had to be in the PTS. I found out that the are in the multiengine PTS but not in the single engine section.

You noticed that...and it's an omission I'd like to correct.

 

[TMetzinger]

Ideally I'd like to see it taught too, at least practicing at low speeds, and then discussing what would and wouldn't be criteria for rejecting a takeoff and what speed limits there would be.

This is covered in multi engine training, and even more when you get into jets. There you've got the three windows - below a certain speed (80 comes to mind) where you will abort the takeoff for any abnormality, above that speed but below or at V1 where you only abort for major failures or loss of directional control ("bells or swerves" comes to mind), and then above V1 you take it into the air.

Some similar logic might apply to singles. You might abort for engine or loss of control at any speed below rotation, but do you really want to abort for a window popping open just before rotation? No answer here, just something to consider.

 

[MauleSkinner]

I'm somewhat hesitant to draw too many parallels between single-engine RTO decision making and what we do in jets...yes, it's probably a good idea to have a cutoff speed for "petty annoyances" like windows and doors popping open, but a lot of what we do beyond that is based on things like minimum runway, brake energy, and some form of "guaranteed performance" in the event of certain specific malfunctions.

Basically, the consequences of a high-speed abort in a jet are far more severe than an RTO in a single, even at or slightly after rotation, and more often than not it's safer to take a problem into the air beyond a certain point in the takeoff than to try to stay on the ground. I don't see a real good parallel to that in single-engine airplanes for the most part.

Fly safe!

David

 

[AuntPeggy]

Would you stop takeoff if airspeed didn't come alive on the runway?

 

[wabower]

Many are oblivious, having been taught that "it will fly when it is ready" and it usually does.

Would you stop takeoff if airspeed didn't come alive on the runway?

 

[deafsound]

I followed the thread about the bent prop/touch and go/full stop landing, and it occurred to me that I've never done a rejected takeoff ever....in training or in real life.
I agree that it should be taught, at least in the same way that spin recovery is taught.

 

[flyingcheesehead]

Would you stop takeoff if airspeed didn't come alive on the runway?

Yup. On the takeoff roll, I call out "Airspeed alive... Gauges are green..." If the airspeed doesn't come alive, I'll probably reject the takeoff unless I'm in a very tight field. I know the plane will fly without an ASI so I'm not going to bend the plane just because the ASI doesn't work, but if I have the room I'll stop.

 

[KennyFlys]

Would you stop takeoff if airspeed didn't come alive on the runway?

Yup. On the takeoff roll, I call out "Airspeed alive... Gauges are green..." If the airspeed doesn't come alive, I'll probably reject the takeoff unless I'm in a very tight field. I know the plane will fly without an ASI so I'm not going to bend the plane just because the ASI doesn't work, but if I have the room I'll stop.

My first concern when I go full throttle for departure is oil pressure. It's followed by a tachometer indication of full power at the expected numbers. Finally as airspeed increases and the needle begins to move away from top vertical, I'll call airspeed alive.

But, if there's no oil pressure... this flight's over. Airspeed is not as much of a concern if you can reasonably ascertain speed by reference to the ground. But, if it's not rotated and starting to climb by the first third (assume 3000-4500') of the runway, again it's back down to the runway.

The power goes to full idle and the nose is held up enough to slow down without losing nose wheel steering in order to have aerodynamic braking. Provided room is available, continue to let the aircraft slow down and transfer to toe brakes but not so to lock the tires and certainly not stop rolling.

Likewise, as soon as the engine is turning at startup, I want the student immediately looking at the oil pressure. If there's not a proper pressure indication, mixture is pulled immediately.

 

[dmccormack]

My first concern when I go full throttle for departure is oil pressure. It's followed by a tachometer indication of full power at the expected numbers. Finally as airspeed increases and the needle begins to move away from top vertical, I'll call airspeed alive.

But, if there's no oil pressure... this flight's over. Airspeed is not as much of a concern if you can reasonably ascertain speed by reference to the ground. But, if it's not rotated and starting to climb by the first third (assume 3000-4500') of the runway, again it's back down to the runway.

Exactly right.

No Oil Pressure, No Fly.

(Though it seems to take a few serves on the runway before most students can glance at Oil Pressure and stay on centerline!)

 

[qbynewbie]

Would you stop takeoff if airspeed didn't come alive on the runway?

Yes. I look for and call out:

* Oil pressure ok
* Oil pressure ok
* Tach is alive
* Airspeed is alive

If any of those aren't what I think they should be, I'll know in plenty of time to abort the landing, even on a short strip, and wouldn't hesitate to do so.

 

[TMetzinger]

I'm somewhat hesitant to draw too many parallels between single-engine RTO decision making and what we do in jets...yes, it's probably a good idea to have a cutoff speed for "petty annoyances" like windows and doors popping open, but a lot of what we do beyond that is based on things like minimum runway, brake energy, and some form of "guaranteed performance" in the event of certain specific malfunctions.

Basically, the consequences of a high-speed abort in a jet are far more severe than an RTO in a single, even at or slightly after rotation, and more often than not it's safer to take a problem into the air beyond a certain point in the takeoff than to try to stay on the ground. I don't see a real good parallel to that in single-engine airplanes for the most part.

Fly safe!

David

Not even single-engine jets? or Turboprops? I can see the point, as you have no balanced-field calculations or performance guarantees in a single, even a jet. If the engine has a problem, you're stuck.

At least for the turboprops I've flown, the PC-12 has published accelerate-stop distances, so you can plan safe runway length with a little better information. The Caravan doesn't.

 

[TMetzinger]

Would you stop takeoff if airspeed didn't come alive on the runway?

Been there, done that. Pitot tube cover was missed on the preflight. Went back, shut down, and did the entire preflight again, because I thought "If I missed the pitot tube, what ELSE did I miss"?

How did I miss the Pitot tube? I had another pilot as a passenger and we were chatting while I did the preflight. Now the only talking I do during a preflight is to EXPLAIN the preflight to interested passengers. Good practice for teaching, and I feel that I do a more thorough preflight when I'm talking it through.

On the takeoff roll, I call "power up - gauges green - airspeed alive - rotate" On this flight it was "power up - gauges green - abort, abort abort".

 

[poadeleted20]

Would you stop takeoff if airspeed didn't come alive on the runway?

Yes (as long as the Horvidos Indians aren't closing in). You should realize that's happening very early in the roll when there's still plenty enough runway ahead to stop without doing what the SP in the original post did.

 

[silver-eagle]

I never did a RTO during training. Of course we talked about it, but doing it is a whole 'nother thing. During my practical, the airspeed didn't come up and I aborted the takeoff. I'm pretty sure it was the DE though he explained it away by saying there must have been some moisture on the tube. Since he cleared the problem himself, we'll never know for sure.
First and only (so far).

 

[poadeleted20]

I never did a RTO during training. Of course we talked about it, but doing it is a whole 'nother thing. During my practical, the airspeed didn't come up and I aborted the takeoff. I'm pretty sure it was the DE...

I wonder how he could have done that. Also, if he did, and something bad resulted, he'd be the apple-mouthed guest of honor at the FSDO's next pig roast -- tampering with an aircraft, etc.

 

[MauleSkinner]

Not even single-engine jets? or Turboprops? I can see the point, as you have no balanced-field calculations or performance guarantees in a single, even a jet. If the engine has a problem, you're stuck.

At least for the turboprops I've flown, the PC-12 has published accelerate-stop distances, so you can plan safe runway length with a little better information. The Caravan doesn't.

Having accelerate-stop calculations really isn't the larger issue...but in most of the jets I've flown, it's entirely possible that if I abort a takeoff near V1, I'm going to set the airplane on fire. I haven't flown a turboprop where that's the case, and I really can't speak to single-engine jets, as I haven't flown them. I'd imagine some of those could have similar issues.

Remember, too, that accelerate-stop and accelerate-go calculations ONLY account for a "simple" engine failure...If you have that situation in a single, you're aborting anyway. It really isn't as cut-and-dried as we like to believe otherwise. If I have an engine fire, and the engine is still making thrust during my deceleration, my a-stop numbers are no good anymore. If I have a piece of sheet metal come loose and go through the engine, my a-go numbers are no good anymore because I have more drag.

I had a flock of birds jump off the runway ahead of me at about 100 knots in a Beechjet once. In my experience, birds jump to engine height before they start to fly away (don't ask). I was above 80 knots, and it wasn't an engine failure, fire, or loss of directional control. But had I continued as normal, it WOULD have been an engine failure at or near V1. I actually rotated about 10 knots early and was able to "hop" over them using ground effect, but the boss' wife DID NOT LIKE IT. She made sure I was aware of that.

What I'm trying to say is that we see jet performance and decision making as this neat little package that we'd like to apply to other operations. It really isn't, and for the most part, applying it would imply ignoring the real issues in RTO decision making, IMO.

Fly safe!

David

 

[dmccormack]

I had a flock of birds jump off the runway ahead of me at about 100 knots in a Beechjet once. In my experience, birds jump to engine height before they start to fly away (don't ask). I was above 80 knots, and it wasn't an engine failure, fire, or loss of directional control. But had I continued as normal, it WOULD have been an engine failure at or near V1. I actually rotated about 10 knots early and was able to "hop" over them using ground effect, but the boss' wife DID NOT LIKE IT. She made sure I was aware of that.

I had a deer cross the runway on an early AM takeoff from EKN after I watched the rest of the herd bound across (always one straggler).

I was nearly 50 knots which is good enough for ground effect but not much else in an Archer. A stop would have turned the prop into a very expensive salad shooter.

So I flew about 3 feet over that very scared quadruped's head. If he'd been a buck he would have lost a few points.

(Imagine that one being explained during hunting season -- "Honest, Sir, it looked like an 8 pointer!")

 

[TMetzinger]

Having accelerate-stop calculations really isn't the larger issue...but in most of the jets I've flown, it's entirely possible that if I abort a takeoff near V1, I'm going to set the airplane on fire.

I assume you mean a brake fire?

Thanks for the enlightening discussion.

 

[wabower]

A pilot who had gotten somewhat lackadaisical about pre-flights and procedures (in his own T-210 that he had owned for ~15 years) showed up at his hangar one evening for a flight review. The ground school included a question regarding the pilot's takeoff procedures and calls, all of which were "by the book."

After the hour of ground school, the pilot rolled the airplane out and performed a thorough preflight (or so he said later) and they taxied out and took off. The instructor sat in the airplane "reviewing the lesson plan" during the entire time the pilot performed the pre-flight inspection.

The takeoff procedures and calls weren't exactly as the pilot had described, and after being airborne and gear-up the pilot noticed the ASI was still on zero.

The departure airport was "closed due to disabled airplane on the runway, expected to re-open in one hour" so the flight was conducted to another airport, with an arc, a hold and an approach. After landing at the destination airport the instructor was unable to find any obstruction, and the ASI worked normally on the return trip.

The pilot said it was one of the best lessons ever, that he learned more about "the numbers" for his airplane during that flight than in his entire period of ownership. During subsequent flights with this same pilot, the instructor noted that his preflight inspections and takeoff calls had improved significantly, as had his awareness of power settings "bottom of the green equals top of the white" and others.

I wonder how he could have done that. Also, if he did, and something bad resulted, he'd be the apple-mouthed guest of honor at the FSDO's next pig roast -- tampering with an aircraft, etc.

 

[Everskyward]

It's been too long ago so I don't remember whether I was specifically taught rejected takeoffs as a private student of if I taught them as a primary instructor. I think it's a good idea, though, to at least have the student apply full power, get rolling for awhile, then stop. Granted, it's not the hardest thing to do but it gets them in the mindset that there is a possibility that it could happen.

I've probably rejected anywhere between 5 and 10 takeoffs (for real) in my life and many more in practice. In singles I had the no airspeed problem a couple times and a no turbocharger problem at least once.

 

[skyflyer8]

Yes, I teach it. And once I did not even have to try too hard, when a deer ran out onto the runway and stopped in front of a student and me.

 

[gismo]

Not even single-engine jets? or Turboprops? I can see the point, as you have no balanced-field calculations or performance guarantees in a single, even a jet. If the engine has a problem, you're stuck.

At least for the turboprops I've flown, the PC-12 has published accelerate-stop distances, so you can plan safe runway length with a little better information. The Caravan doesn't.

I'm trying to understand the value in an accel/stop distance in a single. Obviously if you pick a runway that meets the criteria you should be able to safely stop from the specified speed but so what? If the engine quits just after that you still have a problem so it seems altogether useless to me unless the runway lengths are based on being able to lose the engine at any point in the takeoff and return to the runway safely even it that involves a landing in the opposite direction.

 

[midlifeflyer]

I was curious because I thought for sure RTOs had to be in the PTS. I found out that the are in the multiengine PTS but not in the single engine section.

I think that's because the issues and choices in a twin are a bit different than in a single. It may just be that "Not producing enough power to fly? Stop" in a single is so obvious that no one thought it necessary to have a specific test for it. (Really, it's =is= kind of a "duh!" scenario).

But that said, I agree that the subject should be covered. And I do when I teach. And it's part of my own personal checklist (although all it really says is "Takeoff briefing complete").

Someone asked about really doing it. I did, in an interesting situation. I was doing an intro lesson. We did the run-up and everything was good. I did my pre-takeoff briefing out loud, which included, "in case of an engine failure or signs of an engine problem on takeoff, we will..."

We began the roll and everything looked okay. We rotated and the plane started off the runway. But then it looked wrong and we lost some RPMs. So we did exactly what I had just briefed and re-landed on the remaining runway.

The intro student began taking lessons. He thought what we did and the way it was handled was really cool.

 

[dmccormack]

Someone asked about really doing it. I did, in an interesting situation. I was doing an intro lesson. We did the run-up and everything was good. I did my pre-takeoff briefing out loud, which included, "in case of an engine failure or signs of an engine problem on takeoff, we will..."

We began the roll and everything looked okay. We rotated and the plane started off the runway. But then it looked wrong and we lost some RPMs. So we did exactly what I had just briefed and re-landed on the remaining runway.

What caused the RPM drop?

 

[TMetzinger]

I'm trying to understand the value in an accel/stop distance in a single. Obviously if you pick a runway that meets the criteria you should be able to safely stop from the specified speed but so what? If the engine quits just after that you still have a problem so it seems altogether useless to me unless the runway lengths are based on being able to lose the engine at any point in the takeoff and return to the runway safely even it that involves a landing in the opposite direction.

Here's where it matters.

For a PC12, 6000 ft, 18C, 7716 LBs, 8 KT headwind, 1% uphill slope:

Takeoff Ground Roll: 1475 ft
Total over 50 feet: 2300 ft
Accelerate-Stop: 2950 ft

I've got your kid in the back - what's the shortest runway you want me to use? Without knowing the accelerate-stop, you might have been comfy with 2500-2800 feet. But I bet you're not comfy with less than 3000+, now that you know that if I reject the takeoff right before rotation I may run off the runway.

Accelerate-stop matters for 135 and 121 ops. So does accelerate-go, but that's not an option for singles.

Now some singles may have accelerate-stop distances shorter than their takeoff roll or 50 foot distances (possibly because pistons don't spool up), in which case the distance is moot. I'll ask if that's the case in the Caravan - which may be why an accelerate-stop distance isn't published.

Might be an interesting exercise on a very long runway sometime - practice a rejected takeoff in your airplane and determine a reasonable accelerate-stop distance. If it's longer than your distance to clear 50 feet, then you want to know that, as it should affect your decision making. Aborting a takeoff at rotation speed because there's a belt banging against the fuselage is fine if you KNOW you can stop in the runway remaining - otherwise, take off and come around and fix it.

Hope this explain why the concept is useful even for singles. It helps you to decide what events are valid reasons for rejected takeoffs.

 

[Everskyward]

I think that's because the issues and choices in a twin are a bit different than in a single. It may just be that "Not producing enough power to fly? Stop" in a single is so obvious that no one thought it necessary to have a specific test for it. (Really, it's =is= kind of a "duh!" scenario).

Yeah, but there are other reasons you might want to stop besides engine failure.

 

[gismo]

I can see the usefulness in knowing the point in your takeoff from which you can safely abort (a) without risk of damage, (b) without risk of injury, and (c) without risk of death or serious injury, but I still don't see how an A/S distance gives you that except for the specific scenario used to compute the distance. BTW what is that scenario anyway, rejecting at rotation? Liftoff? Some airspeed?

As to the choice of runways in your example, let's start with a perfectly clear departure path (no obstructions) and for discussion purposes only eliminate all fudge factors (normally I wouldn't want to depart from a runway that just barely met POH requirements). The POH says I'd need 1475 ft, any less and I would be "guaranteed" to fail, any more and the takeoff should be successful if there are no anomalies. Adding more runway to the equation definitely adds options if there is a problem (in addition to allowing for less than perfect techinque, but we are trying to ignore that here) which should improve statistical safety. Even adding 1000 ft would reduce the risk (noticeably) so I guess the question is what's special about 2950 ft given that I'm rather certain 4500 ft would improve it by about as much over the A/S distance. IMO the only time that adding runway length wouldn't provide a proportional increase in safety is when it's long enough that you could gain sufficient altitude to reverse course and land on the runway before going past the point where you could still land straight ahead on the runway. I'll be that's a lot more than 2950 ft under the conditions you posted.

Here's where it matters.

For a PC12, 6000 ft, 18C, 7716 LBs, 8 KT headwind, 1% uphill slope:

Takeoff Ground Roll: 1475 ft
Total over 50 feet: 2300 ft
Accelerate-Stop: 2950 ft

I've got your kid in the back - what's the shortest runway you want me to use? Without knowing the accelerate-stop, you might have been comfy with 2500-2800 feet. But I bet you're not comfy with less than 3000+, now that you know that if I reject the takeoff right before rotation I may run off the runway.

Accelerate-stop matters for 135 and 121 ops. So does accelerate-go, but that's not an option for singles.

Now some singles may have accelerate-stop distances shorter than their takeoff roll or 50 foot distances (possibly because pistons don't spool up), in which case the distance is moot. I'll ask if that's the case in the Caravan - which may be why an accelerate-stop distance isn't published.

Might be an interesting exercise on a very long runway sometime - practice a rejected takeoff in your airplane and determine a reasonable accelerate-stop distance. If it's longer than your distance to clear 50 feet, then you want to know that, as it should affect your decision making. Aborting a takeoff at rotation speed because there's a belt banging against the fuselage is fine if you KNOW you can stop in the runway remaining - otherwise, take off and come around and fix it.

Hope this explain why the concept is useful even for singles. It helps you to decide what events are valid reasons for rejected takeoffs.

 

[wabower]

PC-12 guys continue to learn that single-engine means there is only one out there, and if it quits you are a glider. Local guys have B-350 in pre-buy as a result of such occurrence recently.

I can see the usefulness in knowing the point in your takeoff from which you can safely abort (a) without risk of damage, (b) without risk of injury, and (c) without risk of death or serious injury, but I still don't see how an A/S distance gives you that except for the specific scenario used to compute the distance. BTW what is that scenario anyway, rejecting at rotation? Liftoff? Some airspeed?

As to the choice of runways in your example, let's start with a perfectly clear departure path (no obstructions) and for discussion purposes only eliminate all fudge factors (normally I wouldn't want to depart from a runway that just barely met POH requirements). The POH says I'd need 1475 ft, any less and I would be "guaranteed" to fail, any more and the takeoff should be successful if there are no anomalies. Adding more runway to the equation definitely adds options if there is a problem (in addition to allowing for less than perfect techinque, but we are trying to ignore that here) which should improve statistical safety. Even adding 1000 ft would reduce the risk (noticeably) so I guess the question is what's special about 2950 ft given that I'm rather certain 4500 ft would improve it by about as much over the A/S distance. IMO the only time that adding runway length wouldn't provide a proportional increase in safety is when it's long enough that you could gain sufficient altitude to reverse course and land on the runway before going past the point where you could still land straight ahead on the runway. I'll be that's a lot more than 2950 ft under the conditions you posted.

 

[gismo]

What is a proper Rejected Takeoff?

I'm still stuck on "what is a rejected takeoff" (proper or improper)?

I think this may be clouded by the fact that RTO are historically a transport/jet issue where the decision speed is below liftoff speed. In that case the definition seems pretty clear: RTO= an abort of a takeoff prior to V1. I suppose you could add that a takeoff abort beyond V1 would be "improper", (by the rules) but under some circumstances it might still be the safest option.

But at the other end of the airplane category the definition of a RTO is a lot less clear. If you get a 172 up to 100 AGL then chop the power and land straight ahead is that a RTO? Does it matter whether or not you end up on the runway when stopped or even when touching down? Seems to me that any time you begin a takeoff and stop trying to fly anytime before you reach pattern altitude you have in effect "rejected" the takeoff. And if that's true, I believe the form of a "proper" RTO needs to accomodate the state of the airplane at the point of rejection (pre-rotation, pre-liftoff, airborne at Vx, at Vy, etc) as well as the condition of what lies ahead along the flight path with different criteria for different states. You'd probably need to include the cause of the rejection as well, AFaIK for a jet RTO the cause is assumed to be a complete and/or catestrophic engine failure or something equally severe.

 

[TMetzinger]

I can see the usefulness in knowing the point in your takeoff from which you can safely abort (a) without risk of damage, (b) without risk of injury, and (c) without risk of death or serious injury, but I still don't see how an A/S distance gives you that except for the specific scenario used to compute the distance. BTW what is that scenario anyway, rejecting at rotation? Liftoff? Some airspeed?

In the example, it's rejecting the takeoff at rotation speed.

The point I think you're missing is that without knowing the accelerate-stop distance, you might assume that a 2800 runway is a "good" runway for departure.. It's 500 feet longer than your obstacle clearance distance (2300), right?

So you're tooling along, and right before you pull back - BANG - your prop flies off and your engine is on fire. You stand on the brakes, and overrun the end of the runway by at least 150 feet.

If you'd KNOWN your accelerate-stop distance, then you would have probably chosen a longer runway, and likely stopped while still on the runway, where evacuation and other things would be easier.

YES, if your engine fails after rotation, you are sca-rewed regardless. But I hope you see that knowing the distance can affect your decision-making.

 

[Everskyward]

I think you guys are overthinking this. We are talking about teaching rejected takeoffs to primary students in single-engine piston airplanes, not jets or turboprops. Wouldn't it be nice if maybe a couple times during training the student has the experience of accelerating up to some decent speed then having to stop? This might prepare them for the event where an airplane or animal encroaches on the runway; they don't like some instrument indication in the airplane; or some dumb CFI starts yelling "stop, stop" on the radio.

 

[TMetzinger]

I'm still stuck on "what is a rejected takeoff" (proper or improper)?

I think this may be clouded by the fact that RTO are historically a transport/jet issue where the decision speed is below liftoff speed. In that case the definition seems pretty clear: RTO= an abort of a takeoff prior to V1. I suppose you could add that a takeoff abort beyond V1 would be "improper", (by the rules) but under some circumstances it might still be the safest option.

But at the other end of the airplane category the definition of a RTO is a lot less clear. If you get a 172 up to 100 AGL then chop the power and land straight ahead is that a RTO? Does it matter whether or not you end up on the runway when stopped or even when touching down? Seems to me that any time you begin a takeoff and stop trying to fly anytime before you reach pattern altitude you have in effect "rejected" the takeoff. And if that's true, I believe the form of a "proper" RTO needs to accomodate the state of the airplane at the point of rejection (pre-rotation, pre-liftoff, airborne at Vx, at Vy, etc) as well as the condition of what lies ahead along the flight path with different criteria for different states. You'd probably need to include the cause of the rejection as well, AFaIK for a jet RTO the cause is assumed to be a complete and/or catestrophic engine failure or something equally severe.

A rejected takeoff, to me, is a decision to stop the takeoff before the wheels leave the runway. Multiengine airplanes with balanced-field requirements set that decision point earlier in the roll to the point where V1 is reached.

After you've taken off, you're now performing an emergency landing.

 

[jesse]

In the example, it's rejecting the takeoff at rotation speed.

The point I think you're missing is that without knowing the accelerate-stop distance, you might assume that a 2800 runway is a "good" runway for departure.. It's 500 feet longer than your obstacle clearance distance (2300), right?

So you're tooling along, and right before you pull back - BANG - your prop flies off and your engine is on fire. You stand on the brakes, and overrun the end of the runway by at least 150 feet.

If you'd KNOWN your accelerate-stop distance, then you would have probably chosen a longer runway, and likely stopped while still on the runway, where evacuation and other things would be easier.

YES, if your engine fails after rotation, you are sca-rewed regardless. But I hope you see that knowing the distance can affect your decision-making.

You have your fancy stop-start accelerate numbers. You have enough runway.
You're tooling along, you pull back, you get to 500 feet and BAMK your prop files off and your engine is on fire. You crash into a house off the airport killing everyone on board.

Lance is trying to point out that the number makes sense on big multis because you could have an engine failure where you'd have a decision you'd have to make. In a single if you have an engine failure there is no decision to make with regards to aborting or continuing takeoff. You will be coming to a stop in the near future.

Personally, in a PC-12, I wouldn't hesitate taking off with less than that 2950 feet. The likelyhood that the prop is going to fall off at that moment instead of 10 seconds later is just something you can't plan for or control. It'd have to happen a precise moment for that number to apply any later and you're screwed anyhow.

 

[TMetzinger]

I think you guys are overthinking this. We are talking about teaching rejected takeoffs to primary students in single-engine piston airplanes, not jets or turboprops. Wouldn't it be nice if maybe a couple times during training the student has the experience of accelerating up to some decent speed then having to stop? This might prepare them for the event where an airplane or animal encroaches on the runway; they don't like some instrument indication in the airplane; or some dumb CFI starts yelling "stop, stop" on the radio.

Yes, we're digressing a bit. And yes, I think a student should practice that.

There's a rule of thumb that I don't remember, but it's something about if you haven't reached 60-odd percent of your rotation airspeed by the time you hit midfield, you're not gonna make it. Practicing the rejected take off manuever, say at 40 knots, or 50 (make sure your runway is long enough) is probably a good thing. Have the long runway since you DON'T want to brake the way you would in a real rejection.

 

[TMetzinger]

You have your fancy stop-start accelerate numbers. You have enough runway.
You're tooling along, you pull back, you get to 500 feet and BAMK your porp files off and your engine is on fire. You crash into a house off the airport killing everyone on board.

Lance is trying to point out that the number makes sense on big multis because you could have an engine failure where you'd have a decision you'd have to make. In a single if you have an engine failure there is no decision to make with regards to aborting or continuing takeoff. You will be coming to a stop in the near future.

Personally, in a PC-12, I wouldn't hesitate taking off with less than that 2950 feet. The likelyhood that the prop is going to fall off at that moment instead of 10 seconds later is just something you can't plan for or control. It'd have to happen a precise moment for that number to apply any latter and you're screwed anyhow.

Well then, I think you're accepting an added risk. It's fine to do so, but it's better to KNOW you're doing so. You wouldn't be allowed to do so if you were carrying passengers for hire for the PC-12 operator I know - their specs require the minimum runway length to be calculated based on several factors, and A-S distance is one of them.

My point is it's better to know as much about the airplane as possible. - better info can lead to better decisions. But not if the PIC thinks the info isn't worth anything.

And, by the way, at 500 feet I maintain aircraft control, set the airplane down under control, and we likely all walk or are carried away alive.

 

[MauleSkinner]

I assume you mean a brake fire?

Thanks for the enlightening discussion.

Close...I'll give a little background info for the benefit of those who may not know...

Brakes absorb tremendous amounts of energy in the process of stopping an airplane. This energy is then released by the brake in the form of heat. Lots of it.

If all this heat gets released near the wheel and tire (which it does), the wheel, tire, and the air inside heat up. Increasing the heat of a contained gas increases its pressure, and eventually something's going to give. Jets generally have "fusible plugs" in the wheels. These are a plastic plug that melts at the proper temperature and lets the air out slowly, rather than allowing pressures to build up to where the tire explodes.

We also have "brake energy limits", which equate to the point where as you roll to a stop, your brakes are so hot that they no longer have any effectiveness.

There's a note in the Hawker manual that basically states "if you abort a takeoff at V1, and are brake energy limited, the fusible plugs will release the air in the tires."

So...combining all this, we abort the takeoff, the brakes heat up, the wheels heat up, and the tires go flat (although not right away).

Now we have a flat tire with the hot brake resting directly on the tire. This, then, results in the brake setting the tire on fire. Put the flames out, they come back because the hot brake is still resting on the tire. It'll happen several times. Depending upon the airplane, these flames can be large enough to lick at the bottom of the wing. (Again, don't ask, but it wasn't an RTO ) Of course, there's also the danger of the wheel or brake itself shattering, sending shrapnel all over the place if you give it a good shot with the fire extinguisher while trying to put the tire out. (No, THAT one I haven't experienced.)

OK, so technically you're not always brake energy limited on your takeoff. But say you're in Las Vegas, and get to taxi from the FBO on the northwest corner of the airport all the way to runway 25R...that's about 3 miles, all downhill, at least half of which is with a tailwind. Guess what? You're using your brakes, and you're heating them up. You really have no idea how much brake energy you have left. You could have problems on an aborted takeoff at fairly light weights. As I indicated earlier, it just isn't that nice, neat package that we like to believe.

Fly safe!

David

 

[jesse]

And, by the way, at 500 feet I maintain aircraft control, set the airplane down under control, and we likely all walk or are carried away alive.

That is all you can do--but there are plenty of airports I've flown out of where the likelyhood of a surviable landing with a low altitude failure is pretty small.

Even more so with something big and heavy like a PC-12. The likelyhood of you succesfully landing a 7-10,000 pound airplane in the back of someones yard at 80 mph (or higher) with a blown up engine and 1,000 lbs of fuel during the middle of night is slim. There are plenty of airports out there (lots of urban ones) that would involve you having to do the above.