When to abort takeoff

azpilot

azpilot

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azpilot
I am just full of question lately. Here is a new one.

When you are lining up to take off do you think through what your abort conditions might be ahead of time? On my checklist, one of the last items prior to rolling up to the hold short line is "Initial Heading Review". I usually take an opportunity there to verbalize any conditions that might result in me aborting a takeoff. I am just curious if that is something most of you think about, and if so, what are some of the things you think about?

This Saturday, I am taking my sister and her husband up to KPAN. The field elevation is ~5,150' and the runway is ~5,500' long. The high is forecast to be 60 deg F. I'll be 100 lbs under max gross when taking off from KPAN to come back home. I have flown into the airport before with an instructor, but this will be my first time flying there as the only pilot in the plane.

Looking at the POH, the book says my gnd roll will be 1,440' and the distance to clear a 50' obstacle will be 2,740' (those are conservative numbers without interpolating). There is a taxiway that is basically in the middle of the runway. My plan is to use that taxiway as a go/no go point. If I am not off the ground by that point then something is wrong and I need to abort.
 
Excellent question.

For a high altitude airport, it is very important to identify an abort point. I like to figure out a taxiway, obstacle, light, tower, etc. that I should be at 50 feet before passing. So, for your case, ahead of time, go on Google Earth and find something a bit more than 1/2 mile from the threshold. If you aren't at 50 feet by then, land on the remaining runway. Your taxiway sounds ideal.

Your DA isn't very high, so you should be fine. But, it's a very good practice to have this backup. It's also a good idea to separately mark where you expect to break ground. If you're still on the ground past that, abort the takeoff and figure it out.
 
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Somedudeintn said:
Interesting rule of thumb.
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Yup, the 50/70 rule is pretty standard. If you don't pass it, you need to abort NOW. However, it's not enough by itself to guarantee a good takeoff. It's possible to break ground and remain in ground effect, unable to get out, especially if you rotated early and are behind the power curve.

That's the essential fault this video shows:

https://www.youtube.com/watch?v=ZmEVwyMRYIY

While I normally respect Flight Chops, his diagnosis is not correct on this flight. This was a sea level airport on a hot day, where density altitude was a factor, but not an overpowering factor. The real error was an early rotation and attempt to climb from behind the power curve. In reality, the only thing you can do once that error is made is get the nose down, and with the ground in the way, there isn't much of that to be done.

It would have been much less eventful if that flight had rotated later.
 
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MAKG1 said:
Yup, the 50/70 rule is pretty standard. If you don't pass it, you need to abort NOW. However, it's not enough by itself to guarantee a good takeoff. It's possible to break ground and remain in ground effect, unable to get out, especially if you rotated early and are behind the power curve.

That's the essential fault this video shows:

https://www.youtube.com/watch?v=ZmEVwyMRYIY

While I normally respect Flight Chops, his diagnosis is not correct on this flight. This was a sea level airport on a hot day, where density altitude was a factor, but not an overpowering factor. The real error was an early rotation and attempt to climb from behind the power curve. In reality, the only thing you can do once that error is made is get the nose down, and with the ground in the way, there isn't much of that to be done.

It would have been much less eventful if that flight had rotated later.
Click to expand...

Interesting. While I've never pushed my flying that close, I was a bit surprised to hear the stall horn chirping on the climb out.
 
MAKG1 said:
Yup, the 50/70 rule is pretty standard. If you don't pass it, you need to abort NOW. However, it's not enough by itself to guarantee a good takeoff. It's possible to break ground and remain in ground effect, unable to get out, especially if you rotated early and are behind the power curve.

That's the essential fault this video shows:

https://www.youtube.com/watch?v=ZmEVwyMRYIY

While I normally respect Flight Chops, his diagnosis is not correct on this flight. This was a sea level airport on a hot day, where density altitude was a factor, but not an overpowering factor. The real error was an early rotation and attempt to climb from behind the power curve. In reality, the only thing you can do once that error is made is get the nose down, and with the ground in the way, there isn't much of that to be done.

It would have been much less eventful if that flight had rotated later.
Click to expand...

My POH, under the shortfield section says that I should lift off at 48 KIAS and be at 53 KIAS at 50'. So, if I am going to follow the 'rule of thumb', then I need to be going at least 35 KIAS at the half way point of the runway. Did I do that right? My normal rotation speed is 55 KIAS. 70% of that is 39 KIAS. Both of those numbers seem REALLY slow.

According to the POH, my ground roll should be 660' and I should be at 50' by 1,490'. Now, I completely understand that I will not hit those numbers. This airplane is a 35 year old 172, and I am a pilot with less than 100 hours. That being said, I shouldn't have a problem hitting my normal rotation speed by 2,500'. It might be extra conservative, but if I am not off the ground after having rotated at 55 KIAS by the time I cross the taxi way at mid field, I'll just abort and figure something else out.
 
azpilot said:
My POH, under the shortfield section says that I should lift off at 48 KIAS and be at 53 KIAS at 50'. So, if I am going to follow the 'rule of thumb', then I need to be going at least 35 KIAS at the half way point of the runway. Did I do that right? My normal rotation speed is 55 KIAS. 70% of that is 39 KIAS. Both of those numbers seem REALLY slow.

According to the POH, my ground roll should be 660' and I should be at 50' by 1,490'. Now, I completely understand that I will not hit those numbers. This airplane is a 35 year old 172, and I am a pilot with less than 100 hours. That being said, I shouldn't have a problem hitting my normal rotation speed by 2,500'. It might be extra conservative, but if I am not off the ground after having rotated at 55 KIAS by the time I cross the taxi way at mid field, I'll just abort and figure something else out.
Click to expand...

I've never used the 50/70 rule, but I would suggest only using it as a never-less-than reference. I would not use it as a go/no go reference. It doesn't provide you with enough information. It seems like a handy cross check, but not s planning tool.

It sounds like your airborne by midfield idea is a safe way to handle it.
 
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azpilot said:
My POH, under the shortfield section says that I should lift off at 48 KIAS and be at 53 KIAS at 50'. So, if I am going to follow the 'rule of thumb', then I need to be going at least 35 KIAS at the half way point of the runway. Did I do that right? My normal rotation speed is 55 KIAS. 70% of that is 39 KIAS. Both of those numbers seem REALLY slow.

According to the POH, my ground roll should be 660' and I should be at 50' by 1,490'. Now, I completely understand that I will not hit those numbers. This airplane is a 35 year old 172, and I am a pilot with less than 100 hours. That being said, I shouldn't have a problem hitting my normal rotation speed by 2,500'. It might be extra conservative, but if I am not off the ground after having rotated at 55 KIAS by the time I cross the taxi way at mid field, I'll just abort and figure something else out.
Click to expand...

I wouldn't even bother with the rule with that kind of runway length. You'll probably rotate well before the midpoint. If you're not at 50-55 knots by the middle of the runway, something is wrong with the airplane or it's significantly overloaded.
 
fiveoboy01 said:
I wouldn't even bother with the rule with that kind of runway length. You'll probably rotate well before the midpoint. If you're not at 50-55 knots by the middle of the runway, something is wrong with the airplane or it's significantly overloaded.
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That's exactly what I was thinking king as well.
 
azpilot said:
This Saturday, I am taking my sister and her husband up to KPAN. The field elevation is ~5,150' and the runway is ~5,500' long. The high is forecast to be 60 deg F. I'll be 100 lbs under max gross when taking off from KPAN to come back home. (...)
Looking at the POH, the book says my gnd roll will be 1,440' and the distance to clear a 50' obstacle will be 2,740' (those are conservative numbers without interpolating).
Click to expand...
Numbers say clearly that you have plenty of margins. Good of you to look at them, not eyeball it. I have just 2 comments.

#1: Don't put too much stock into this:
azpilot said:
There is a taxiway that is basically in the middle of the runway. My plan is to use that taxiway as a go/no go point. If I am not off the ground by that point then something is wrong and I need to abort.
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If you focus on this decision point, you may forget to focus on something else. I would just fly the airplane and trust the book. Abort if there's an obvious lack of power, loud noise or vibration, smoke, or lack of RPM. Typically you can see that happening within 1000 ft of roll. You must keep many excuses to abort in mind, not just the runway length remaining.

#2. Good job calculating runway lengths, but 5k may be about time to consider the rate of climb as well. This is important. I knew a few cases when airplane could not outclimb raising terrain after a successful takeoff. Above 8k for sure you need to plan a flight into flat or descending terrain, just in case.
 
I just had to abort a TO a few weeks ago. The runup was fine, but after pushing up the power I noticed a red alternator light. There was a moment where I considered continuing, but it was a three hour flight with much of it in IMC, so even though I have dual alternators and dual and independent buses, I elected to abort.

All of this occurred and I was able to stop within half the distance of a 4800 foot runway. Turned out it was a broken field wire. Even though there is more than enough power to run everything from one alternator, it wasn't worth the risk. Anyway, not really a big deal overall.
 
Pete, You make good points. I did look at the rate of climb in the POH as well. With the conditions that are forecast and the weight I expect we'll be at, the book is saying 450 fpm. I am feeling pretty good about the flight right now. I double check all the numbers with the actual weather the morning of the flight just to be sure.

I'll come back on Saturday to let everyone know how it goes!
 
AcroBoy said:
I just had to abort a TO a few weeks ago. The runup was fine, but after pushing up the power I noticed a red alternator light. There was a moment where I considered continuing, but it was a three hour flight with much of it in IMC, so even though I have dual alternators and dual and independent buses, I elected to abort.

All of this occurred and I was able to stop within half the distance of a 4800 foot runway. Turned out it was a broken field wire. Even though there is more than enough power to run everything from one alternator, it wasn't worth the risk. Anyway, not really a big deal overall.
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Yikes!!! Good call on the abort. During my very first flight after earning my certificate, I had a complete electrical failure in class Delta airspace (no radio, no transponder, no lights, no flaps). It was quite the experience. I definitely don't want to have to deal with that again. At least it was in VFR daylight conditions.
 
I use it in my multiengine book, but it applies equally to the situation you pose. I call it constructive paranoia. As I roll into position, I tell myself that the engine will quit before I get to rotation speed; if I make it to rotation speed I tell myself that the engine will quit before I am 100' agl; when I pass through 100' agl I tell myself that the engine will quit before I get to pattern altitude. This has actually worked for me when I had engine anomalies (no outright failures) during takeoff in twins...I did the right thing because my mindset was that it was going to happen, so be prepared. Always be mentally prepared for what might happen.

My only actual engine failure was at 14000 feet in a twin and was a non-event...except when it came time to taxi with one engine shut down.

Bob Gardner
 
Check out this video.
https://www.youtube.com/watch?v=WbqDTuAQoi4

I thought this guy had plenty of time to just sit her back down. Listen to his gasp at 2:55 when he realizes the engine stumbled. He hyperventilates and flies over the runway/clear area til 3:25 (that's 30 seconds). At close to 90 knots that was 3/4 of a mile he had to sit it down.

Panic is a terrible thing and I could understand panic if he was immediately over water or trees. He was in the clear. All he had to do was kill power and land.

I'm a low time student pilot. What am I missing?
 
That didn't look like a panic to me. He set it down in a field just fine. It might have been nice to set it down at the airport, but it is in no way essential. At least at that airport. Sometimes they are hemmed in by development.

A panic looks like a wing dipping followed by a big fireball.
 
Gotcha

I was going by the breathing and seemingly frozen state til he finally said "F I gotta sit this thing down".

I agree, any safe landing is not a panic.
 
That video was posted by a member here. From what I saw, he didn't really have much time to get it down on the field once the engine started stumbling. There are usually fences at the end of the field, so you don't want to possibly overrun and hit that.

He had partial power and did the right thing in that situation, keep it flying, shallow turns only and found a nice spot to put it down that was more or less straight ahead.

Interestingly enough I believe the cause was fouled/worn spark plugs.
 
Yes, I'll be in N6291D on Saturday.
 
bobmrg said:
I use it in my multiengine book, but it applies equally to the situation you pose. I call it constructive paranoia. As I roll into position, I tell myself that the engine will quit before I get to rotation speed; if I make it to rotation speed I tell myself that the engine will quit before I am 100' agl; when I pass through 100' agl I tell myself that the engine will quit before I get to pattern altitude. This has actually worked for me when I had engine anomalies (no outright failures) during takeoff in twins...I did the right thing because my mindset was that it was going to happen, so be prepared. Always be mentally prepared for what might happen.

My only actual engine failure was at 14000 feet in a twin and was a non-event...except when it came time to taxi with one engine shut down.

Bob Gardner
Click to expand...

Bob, that's some great advise. It so much easier to make a good decision, if you have already played out the scenario in your mind and are mentally prepared for it to happen.
 
I've had two GA aborts that where both engine related and 1 airline abort. I tell my students to abort on the runway before rotation for anything abnormal. After rotation it becomes a game of where to go depending on the airport and your situation.

At my home field if you lose an engine on 4, after takeoff, you have almost no choice but trees. If your high enough you can make a deer hunting clearing along an old pipeline.

A few weeks ago I asked for an abort but we decided it wasn't logical nor safe. We had the cockpit door swing open on the roll. I was flying that leg so I asked the Captain if he wanted to abort. The answer was no it's not important. It all happens in about a time span of a few seconds.
 
evapilotaz said:
Cool! There will be some afternoon winds but you will be out of there by then. Enjoy the flight and scenery up there.
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I'm taking my GoPro. We'll see if my landings are any better this time. :yes:
 
ARFlyer said:
A few weeks ago I asked for an abort but we decided it wasn't logical nor safe. We had the cockpit door swing open on the roll. I was flying that leg so I asked the Captain if he wanted to abort. The answer was no it's not important. It all happens in about a time span of a few seconds.
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I had a cockpit door fly open on a 757 trip last year - takeoff roll, my leg. Big noise, both of us look over the shoulder quickly then back to work. I think he said 'doors open', I said 'yep'. That was it. A flight attendant jumped up and shut it - debriefed her on that later. :nono:
 
Figure out acc / stop and acc/ go and then give yourself a balanced field. Then rotation is your go/no go barring engine failure.
 
We had a great flight from KCHD to KPAN on Saturday. I took my sister and her husband up there. We stopped in at the Crosswinds restaurant and I picked up a Banana Cream pie that I am pretty excited to eat this afternoon.

We experienced a little bit of turbulence on the way there. I probably should have climbed a little higher. The wind was whipping off the Matazals, and I am pretty sure that is what caused the turbulence.

The landing??? Well... I landed... and we were all safe. I'll see if I can get a video posted. Videos are a lot of work.

As for departure, the airplane performed very closely to what the POH said it would do. I was was well of the ground and climbing by the time I got to the midfield point I had designated as my abort point. I was climbing at about 400 fpm on the departure leg.

We flew home at 8,500 feet and stayed above all the turbulence. I transitioned the delta airspace at KFFZ on the way home back to KCHD and made a long straight in for 22R back home. It was a fun trip!
 
No abort necessary. The plane performed (pretty much) as expected per the POH.

I am working on the two-hand-on-the-yoke. I realized that somehow I have developed the habit of putting my right hand on the yoke as soon as I go power to idle, and I know I have the runway made. In the first landing, I realized this right at touchdown, and you'll see my right hand go back to the throttle. I did the same things back at KCHD, but I recognized it sooner. I'm learning...

 
Walboy said:
Thanks for sharing the video. Nice job!
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Thanks Walboy! It was a fun flight. That is the furthest I have 'stretched my wings' since I got my private back in July. It was a cross country flight with two passengers to a airport in the mountains. I did class delta transitions through two different airports (Gateway on the way up, and Falcon on the way home).

It was a little bittersweet though. That is likely the last time I'll fly N6291D. I really grew to love that airplane, even though it did have that electrical failure back in August. It will always be the plane I flew during my private pilot checkride. Wings270 is going through some major changes, and I am not sure if I will ever be able to fly it again. Definitely bittersweet...
 
I will miss 91e even though I flown all the wings 172 91e became my fav.
I don't know why wings270'doensnt just hire a manager to run the business and keeps the doors open. Anyway that is beyound the scope of this thread.
 
I have only aborted a takeoff one time. I was rolling down the runway and the airspeed wouldn't come alive
 
TheGolfPilot said:
I have only aborted a takeoff one time. I was rolling down the runway and the airspeed wouldn't come alive
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I've had several. On one, a 182 engine stumbled when advanced; in retrospect, it was way too fast. On another, a 172 wouldn't make adequate RPM when starting the roll. On another, a no-flap takeoff on a 177RG settled back to the runway after rotation. On a fourth, an Archer developed a nasty shimmy and a growling noise during the roll at ~30 knots. Turned out to be a failing wheel bearing.
 
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