Poll; Ground roll timing

What is your most common or typical take-off roll time?

  • 0-10 secs

    Votes: 29 51.8%

  • 11-30 secs

    Votes: 24 42.9%

  • 31-60 secs

    Votes: 1 1.8%

  • 61-90 secs

    Votes: 0 0.0%

  • 91-120 secs

    Votes: 1 1.8%

  • 121+ secs

    Votes: 1 1.8%
  • Total voters
    56
Let'sgoflying!

Let'sgoflying!

Touchdown! Greaser!
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Dave Taylor
Have you ever timed your takeoff roll? For any piston, fixed-wing aircraft.
I am curious what the range of times people are seeing, regardless of aircraft type, or configuration, whether it be heavy or light, hi or low DA, headwind/tailwind etc etc. Just a really rough discovery of ranges would be of interest to me. It's got to be somewhere from 5 seconds (stol a/c) to what, 90 seconds?
Regardless of whether you think it is a useful number or not.
 
Let'sgoflying! said:
Have you ever timed your takeoff roll? For any piston, fixed-wing aircraft.
I am curious what the range of times people are seeing, regardless of aircraft type, or configuration, whether it be heavy or light, hi or low DA, headwind/tailwind etc etc. Just a really rough discovery of ranges would be of interest to me. It's got to be somewhere from 5 seconds (stol a/c) to what, 90 seconds?
Regardless of whether you think it is a useful number or not.
Click to expand...

Never done that. I’ll give it the ol’ one Mississippi, two Mississippi next time I go flying and get back
 
I'm rolling when I come off the taxiway to the runway, when I'm lined up I ease in the throttle. When should I start counting?
 
I count during every takeoff in an airliner and it is 30 seconds... 40 if a hot takeoff for a 15 hour flight (Dubai to SFO).
 
<snaps fingers> dang, I've been doing it all wrong. I should have been watching the clock instead of the ASI?

I'll do the one Mississippi thing too just for S&Gs.
 
In the Mooney (280hp, 3368lb MGW, Vr 70 KIAS), I would guess about 10 seconds. In the TBM 900 (850shp, 7394lb MGW, Vr 85 KIAS), more like 20 seconds. In the TBM 850, (same numbers as the 900 except only 700shp available for takeoff), longer yet. I'm flying it tomorrow, I'll have to pay attention.
 
5ish seconds.

Less if I do it "wrong" and start rolling power in as I am making the turn from the taxiway - though I guess it depends on when you start counting.
 
I haven't actually "timed" it, but looking back at the flight data, on the last three flights from when the ground roll starts to when I see change in GPS altitude is 21 seconds (+/- 2 seconds).

But bear in mind that I don't pull back on the stick until I hit 65kts and my ground roll is a slow start where I begin the roll at reduced power.
 
According to 2d = vt around 12.8 seconds from a dead stop. I haven't run the stopwatch
 
Somewhere between "everything is good" and "hey, I'm past the midway point".

But it changes by temperature and load, so there is no one number.
 
As a student, I hung out near the approach end of the runway, and I timed people at the beginning of base turn to landing and separate final turn to landing to determine what was safe as far as departing in front of another aircraft. Most took 90-120 seconds from the base turn ... the guys practicing power off 180's took right near 60 seconds.
 
danhagan said:
As a student, I hung out near the approach end of the runway, and I timed people at the beginning of base turn to landing and separate final turn to landing to determine what was safe as far as departing in front of another aircraft. Most took 90-120 seconds from the base turn ... the guys practicing power off 180's took right near 60 seconds.
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That is right on the money, Dan!
Some think there is no reason to be interested in the takeoff time. I understand that. In fact I anticipated that (to no effect of course, lol) in my OP.

The whole reason for me starting this thread was that someone was turning base as I powered up for takeoff.
I thought there was scads of room.
He apparently disagreed, and started a butthurt conversation with someone else in the pattern about being cut off. This was in a rural airport, where I suspect, the pilots are used to having the entire county to themselves and don't realize how aircraft can efficiently use the airspace with spacing closer than 2 miles in the pattern.
Anyway I was off well before he could even have gotten near the runway and safety was not compromised.
The timing you and others have provided has further shown me that.
I wish I could have had a one-on-one conversation with him about it.
I don't want to aggravate or inconvenience another pilot and I am willing to change my ways if I am shown to be wrong.
In my humble opinion, he might have noticed my calls taxiing, my presence at the hold line and perhaps extended downwind 5-10 seconds so as to avoid his perception of a conflict. I have provided the same courtesy many times.
 
Why would you time it? I've been flying for over 45 years in lots of different aircraft and it has never occurred to me that time until lift off had any meaning whatsoever.

A Cub can be off the ground in 5 or 6 seconds, but it's still an obstacle for a landing aircraft. An F18 in that same amount of time will never be a factor unless you're also in an F18. It''s all about distance, not time.
 
This is common for backcountry ops and really should be common for anyone operating from short fields. I know that when my plane is light and at low DA, it takes and 8 or 9 mississippi count. When I’m heavy and hot/high DA, it can take as long as 17. This is a pretty useful gauge for knowing if you need to abort a takeoff.
 
Most small piston planes under 10

Turbine would be the next option up, 10-15ish
 
AA5Bman said:
This is common for backcountry ops and really should be common for anyone operating from short fields. I know that when my plane is light and at low DA, it takes and 8 or 9 mississippi count. When I’m heavy and hot/high DA, it can take as long as 17. This is a pretty useful gauge for knowing if you need to abort a takeoff.
Click to expand...

This right here.

If something is off, I can abort. If I fly enough, it should “feel” obvious, but I don’t, so a count is helpful. I’m usually up by the end of the second stripe at my home field. Looks like 11 seconds from the video (0:17 to 0:28)

 
AA5Bman said:
This is common for backcountry ops and really should be common for anyone operating from short fields. I know that when my plane is light and at low DA, it takes and 8 or 9 mississippi count. When I’m heavy and hot/high DA, it can take as long as 17. This is a pretty useful gauge for knowing if you need to abort a takeoff.
Click to expand...
A much more reliable and accurate method is Sparky Imeson's formula (mathematically based, but don't ask me the details) that's based on reaching 70% of lift off speed at 50% of the runway, which gives you a specific point to abort if you have not reached a specific speed and still allows adequate stopping distance on the remaining runway.

Again, time is not the relevant metric. It's speed and distance that's used in the decision making.
 
Capt. Geoffrey Thorpe said:
Correct. We don't use the metric system in aviation.

But, sometimes we get curious about not useful things. Eh?
Click to expand...

We do.

What scares me is that people take "not useful things"and then apply them to critical decision making in aviation. :eek:
 
dbahn said:
What scares me is that people take "not useful things"and then apply them to critical decision making in aviation. :eek:
Click to expand...
Actually, counting potatoes is a legit STOL technique.

One Potato, Two Potato, Three Potato, Flaps Potato, Rotate...
 
dbahn said:
A much more reliable and accurate method is Sparky Imeson's formula (mathematically based, but don't ask me the details) that's based on reaching 70% of lift off speed at 50% of the runway, which gives you a specific point to abort if you have not reached a specific speed and still allows adequate stopping distance on the remaining runway.

Again, time is not the relevant metric. It's speed and distance that's used in the decision making.
Click to expand...

I’m aware, I just personally don’t find it very practical.
 
It took 17 seconds until I rotated at 65. Airport elevation 5660.5 ft Cessna R182, I guess I could have slammed the throttle forward and that would have shaved off .5 seconds.
 
Let'sgoflying! said:
That is right on the money, Dan!
Some think there is no reason to be interested in the takeoff time. I understand that. In fact I anticipated that (to no effect of course, lol) in my OP.

The whole reason for me starting this thread was that someone was turning base as I powered up for takeoff.
I thought there was scads of room.
He apparently disagreed, and started a butthurt conversation with someone else in the pattern about being cut off.
Click to expand...

Reason I timed it back then was because our field had a TON of student pilots when I was learning (up to 6 in the pattern with other planes shoe horning in on the 45). You could essentially sit at the hold short for an hour if you didn't know how to get out without messing anyone up. We had some TIGHT departures ... in a normal pattern, without ANY delay, you should be airborne if the approaching plane is right at the turn to final ... but don't depart if they say power off 180 or simulated engine out base to final.
 
ateamer said:
RV-8A, 180 horsepower, constant speed, 25’ MSL, 91 degrees and humid: 10 seconds from brake release to liftoff at 55 KIAS.
Click to expand...

So about a 450' ground roll then?
 
I always thought timing the takeoff run was a seaplane thing.

I'm definitely a fan of observing ground roll distance on every take off and comparing that with what I expected. I use runway remaining markers (duh) and any paint stripes (500', 1000', individual centerline stripes, etc) and at least make a mental note. You can use the measurement feature of google maps to get an accurate number.

You catch issues with engine performance and takeoff configuration errors automatically this way. For any medium/high density altitude operations it gives you a chance to check calculated with actual takeoff distances, which is information that can keep you off of the evening news someday.

I just reviewed some footage and it appears 6 seconds for a takeoff run in my flapless Citabria.
 
It varies with density altitude, head wind, gross weight, CG, runway surface and grade. Heck a time in the morning will not equal a time in the afternoon
 
Fortunately they're a thing called math to reconcile those differences down to the foot of necessary
 
Looking at the poll, I’m waiting for the 2 minute ground roll post in a GA plane. Averaging the ground roll speed...

65 mph * 120 sec = 2.167mi ground roll or 11,440’ of runway.
 
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NordicDave said:
Looking at the poll, I’m waiting for the 2 minute ground roll post in a GA plane. Averaging the ground roll speed...

65 mph * 120 sec = 2.167mi ground roll or 11,440’ of runway.
Click to expand...

That's only if it's already rolling at 65mph to start.

The distance formula from 0 to takeoff speed is 2d = v * t where d is feet and v is ft/s

d = v0t * 1/2 at^2
v = v0 + at

since v0 = 0 we can drop those terms.

d = 1/2at^2
v = at
we don't care about acceleration rate so a = v/t and substitute
d = 1/2(v/t)*t^2
one of the t's cancel
d = 1/2vt
2d = vt

65mph at 120 seconds gets you 5,720' - still a long ass takeoff roll for a GA plane.
 
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EdFred said:
That's only if it's already rolling at 65mph to start.

The distance formula from 0 to takeoff speed is 2d = v * t where d is feet and v is ft/s

d = v0t * 1/2 at^2
v = v0 + at

since v0 = 0 we can drop those terms.

d = 1/2at^2
v = at
we don't care about acceleration rate so a = v/t and substitute
d = 1/2(v/t)*t^2
one of the t's cancel
d = 1/2vt
2d = vt

65mph at 120 seconds gets you 5,720' - still a long ass takeoff roll for a GA plane.
Click to expand...

I was using quick throwaway math on a work break thus the average of 65 mph. Maybe another way to look at this is full rotation out of ground effect at 90-100mph. Starting from zero and accelerating to 90 mph in 120 seconds. Assuming a high density allude scenario to justify the long ground roll, the rotation speed would need to be much higher than seal level. I don’t know, just messing around here...

Final speed 90mph starting speed 0 so V=90mph rate of acceleration to 90/120 sec is .75, so 8,100’ of runway assuming no obstacles to clear.

Thanks Ed for pursuing more precise math for an estimate.
 
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