[Full Metal Jackass]

Rule of thumb: If you don't have 2/3 of rotate speed by 1/3 of runway length, abort.

Really? So I have to reach 45 knots within 200m? Then each take off attempt I try at my home field will be an aborted take off.

[Lefty]

In a privately operated light GA aircraft, there are no hard and fast rules.

The rules of thumb mentioned above are reasonably accurate but you can buy either an electronic or mechanical take off distance calculator which will factor in runway surface, wind strength, % of MAUW etc, and give you the estimated distance for your ground roll and reaching 50’ agl.

You should then (ideally) not attempt a takeoff if your calculated takeoff distance is greater than 2/3 of the available runway length.

The other way of measuring your actual takeoff distance is by reference to an accurate airfield diagram - and using the distance from the threshold to each runway intersection as a guide. Most airfields have such a map.

For example, Waltham have been using r/w 21 for the past few days, and (in my Cherokee Six), I try to be just lifting off (and landed and stopped) before the intersection with r/w 25. Can’t do it in a Warrior though!

[masterofnone]

When to abort? When it feels instinctively "wrong".

There are two possible cues.... physical and instinctive. With a reasonably well calibrated pilot, instincts typically start ringing alarm bells well before physical cues become apparent.

That said, personal experience has revealed that initial instincts can't always be relied upon to stop you getting into a problem, even if they are good enough to get you out of it. Accordingly physical cues are an important backup, and I've always been amazed at the lack of distance markers on runways.

Unsurprisingly, this topic has been done before (see here and here). As you'd expect, a wide variety and strength of opinions exists out there

[PaulB]

The rules of thumb mentioned above are reasonably accurate but you can buy either an electronic or mechanical take off distance calculator which will factor in runway surface, wind strength, % of MAUW etc, and give you the estimated distance for your ground roll and reaching 50’ agl

I’ve wondered and was thinking of asking if there were any electronic performance apps (or similar) to replace those (seemingly) photocopied graphs in POHs, but wondered whether they were too aircraft specific.

It does seem that such things exist, though..... but I’ve never seen any. Are they available/reliable etc.

[BobD]

The rules of thumb mentioned above are reasonably accurate but you can buy either an electronic or mechanical take off distance calculator which will factor in runway surface, wind strength, % of MAUW etc, and give you the estimated distance for your ground roll and reaching 50’ agl

I’ve wondered and was thinking of asking if there were any electronic performance apps (or similar) to replace those (seemingly) photocopied graphs in POHs, but wondered whether they were too aircraft specific.

It does seem that such things exist, though..... but I’ve never seen any. Are they available/reliable etc.

https://appadvice.com/app/gasco-perform ... /942306086

[PaulB]

Thanks, I’ve previously seen that one.... what I was thinking about was an aircraft specific app that gave the unfactored TODR, to avoid having to use the charts in the POH.

[Grelly]

Personally, I start filling my nappy when I pass the half way point and my wheels are still on the ground!

[cotterpot]

Thanks, I’ve previously seen that one.... what I was thinking about was an aircraft specific app that gave the unfactored TODR, to avoid having to use the charts in the POH.

this one for C172

https://appadvice.com/app/c172-performance/741721884

[defcribed]

For example, Waltham have been using r/w 21 for the past few days, and (in my Cherokee Six), I try to be just lifting off (and landed and stopped) before the intersection with r/w 25.

Much the same for me, but substitute r/w 29 where Lefty has r/w 25.

[Lefty]

Thanks, I’ve previously seen that one.... what I was thinking about was an aircraft specific app that gave the unfactored TODR, to avoid having to use the charts in the POH.

There are apps that are specific to one aircraft type. However it is still generic to that aircraft type. You will still need to extract the exact ISA performance figures from your aircraft POH and enter it into the app the first time you use it. Thereafter, the app calculates the takeoff and landing performance for the specific conditions, as factors of the ISA performance.

[MichaelP]

I teach students to do a takeoff roll calculation based on the Performance table if there is one, and likewise a landing roll calculation.

Put the takeoff roll and landing roll together and compare this combined distance with the runway/strip distance available.

If the combined distance is less than the ground run available then be airborne by the halfway point or close the throttle.

If the combined distance is more than the ground run available then have 70-75% of your airspeed by the halfway point. This is your go/no go decision point.
Be disciplined, and stop if you have not reached the desired speed.
Go back and think about it.

Remove weight, fuel/baggage, passengers, if you absolutely have to go, but still be disciplined if she still won’t get out of there. Phone the mechanic, arrange a trailor.

http://www.mpaviation.com/lessn12.htm

http://www.mpaviation.com/gayro.htm

Also consider the departure path and the climb gradient required. What obstacles do you face?
What will the wind do to you as you rise above these obstacles?
Do you have an ‘out’?

[Gertie]

Hopefully obvious but I'll say it anyway....

.... on long runways, throw the rule of thumb out the window, whatever it is.

Yeah, with 2km you can often abort and land back and stop on the runway provided you're still below around 300'

[Dave Phillips]

Disagree, a bit.

I regularly operate from 14000+ft runways in an MEP. I’ll (almost) always use full length. It’s not just about the ‘getting airborne’ bit, it’s also about getting as much height as possible before being over places you don’t want to crash. Height is king - ask any glider pilot.

[T67M]

You can only have too much runway length when curvature of the earth needs to be considered.

I'm constantly amazed that pilots at Redhill are prepared to start their takeoff roll on runway 18 at the 150m displaced landing threshold. Runway 18 points straight at Gatwick, so the crosswind turn must be flown very shortly after the airfield boundary. From the full length, most aircraft make 400ft - but less than 300ft from the displaced threshold. I know that I can "land back on" with 850m and stop before the hedge (don't ask how I know this!) - but from 700m it would be a different story.

[akg1486]

As mentioned, this was perhaps not a unique topic; I have to confess I didn't do as diligently a search as I should have before starting the thread. Nevertheless, many interesting thoughts on the topic. Thanks for that.

The main theme serms to be that one aborts when "it doesn't feel right". I usually abort halfway if I'm not confident I'll make it. But that call is made with a gut feeling.

So far, I've aborted T/O runs that might have been successful, but not yet failed to abort when I should have. I don't have tons of experience (some 450 hours) but so far so good. I estimate 70% of my take-offs are from 2 km asphalt where there are no aborted takeoffs unless there are mechanical issues.