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Whenever I fly on a turbofan-powered airliner, I always notice how much acceleration there is, which seems like more than any car I've ever owned could do. (That might be an illusion, I realize; acceleration always seems higher to a passenger than to the person pushing the throttle.) I marvel at the power needed for that much acceleration of such a huge aircraft full of passengers, fuel, and cargo.

What is a typical maximum horizontal acceleration of a turbofan-powered airliner during takeoff? (Perhaps I should see if there's an app for my mobile phone that can measure and display acceleration before I fly next.) I'll gladly accept measured real-world values, but if someone wants to calculate an answer, let's assume that we're talking about a Boeing 767-300 on runway 8R at Hartsfield–Jackson Atlanta International Airport, which is 9,999 feet (3,048 m) long. We can also assume that the pilot runs up the engines to the takeoff throttle setting with the brakes on and then releases the brakes suddenly, just to simplify the calculation. (I realize that airline pilots typically ramp up the throttle slowly to avoid alarming passengers.)

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    $\begingroup$ I think you’d be surprised how low it actually is. Not sure what kind of cars you have owned, or how hard you drive them, but look up the 0-60 times for sporty cars. Some may have even more useful 0-100 times published. Clock the roll next time you fly. Guesstimate 60mph as best you can. Guess how fast you are going at 3, 5, & 10 seconds. I think you will find that airliner takeoff rolls are actually kind of sluggish by comparison. You probably notice it more because you are thinking about it, and normally drive gently. $\endgroup$ Feb 25 at 1:48
  • $\begingroup$ Maybe what seems surprising is the "broad power band": the acceleration of a jet starts right away, without a delay for the RPMs to rise, and no pauses for shifts, and it lasts much longer because the top speed of a jet is much higher than a car's. By the way, I've always had trouble estimating speed down the runway because I'm sitting up much higher than when I'm in a car. That's one of the reasons I'm asking. Now that I think about it, I could use an "angle finder" like this one as a crude accelerometer next time. $\endgroup$
    – rclocher3
    Feb 25 at 2:22
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    $\begingroup$ @rclocher3 Ramping up the throttle slowly is hardly meant to not alarm passengers. It's better for the engine and avoids compressor stall. Most modern engines ramp themselves up, regardless of how hard you ram the throttle. $\endgroup$
    – user55607
    Feb 25 at 5:13
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    $\begingroup$ @rclocher3 There’s an accelerometer in your phone… $\endgroup$
    – Koyovis
    Feb 25 at 7:52
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    $\begingroup$ there are also apps that will read the accelerometer in your phone and display the info in pretty pictures and graphs. $\endgroup$
    – FreeMan
    Feb 25 at 16:47

3 Answers 3

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  1. Calculation

    From the wiki page for a B767-300

    • MTOW = 158.8 ton, OEW = 86.1 ton
    • Max thrust = 2 * 270 kN

    So at MTOW: a = F/m = 540/158.8 = 3.4 m/s$^2$ = 0.35g

    At OEW = 540/86.1 = 6.27 m/s$^2$ = 0.64g

    When releasing the brakes at full throttle, acceleration transitions from 0 to the above immediately. It is pretty much the maximum acceleration, since at brake release the drag is still zero.

    For comparison: my 1999 Holden Commodore is quoted as reaching 100 km/h = after 8.9 seconds.

    a = v/t = (100 / 3.6) / 8.9 = 3.1 m/s$^2$

  2. Data from a flight simulator, current passenger aeroplane twin-jet

    enter image description here enter image description here

  3. Compared to road vehicles...

    enter image description here

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    $\begingroup$ Right, but airliners don't typically take off at maximum thrust. The pilots calculate how little thrust they can use given the load, the air temperature, and the length of the runway, and then they set the throttle there, in order to maximize the life of the engines. $\endgroup$
    – rclocher3
    Feb 25 at 2:35
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    $\begingroup$ If they choose to use flex thrust. Not always. Depends on the airline's policy, and in the end what the Capt wants to do. Some pilots don't like to use flex because every takeoff has that short field "end of the runway looming" feeling, even though you are technically within accelerate/stop margins. $\endgroup$
    – John K
    Feb 25 at 4:48
  • $\begingroup$ Flex or de-rate is almost always used, if available (per performance calculations). Most runways are long enough that you rarely get that "end of the runway looming" feeling. In narrowbodies at least, heavies may be different, haven't flown one. $\endgroup$
    – Khantahr
    Feb 26 at 18:34
  • $\begingroup$ So the simulated peak acceleration of 0.35 g, which matches the acceleration at MTOW at full throttle, corresponds to a zero-to-sixty-mph time of 7.9 s, or 0 to 100 km/h in 8.2 s. That's just a little faster than my Mazda Miata (MX-5), which was allegedly capable of zero to sixty in 8.1 s when it was new. (I know that I'm comparing a peak value to an average value, but I don't have acceleration vs time graphs for a Miata. I could probably make such a measurement, but I don't want to brutalize my clutch.) $\endgroup$
    – rclocher3
    Feb 28 at 21:17
  • $\begingroup$ By the way, the 3'4" (3:04) YouTube video in the web page linked in the answer is here. The spoken language in the video is Turkish, but I got English subtitles when I watched it. Well worth watching. $\endgroup$
    – rclocher3
    Mar 1 at 16:15
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As the speed increases, the drag increases, but the tire friction and thrust decrease. There's no simple equation; manufacturers rely on iteration and flight data to produce the ready-to-use performance data.

The acceleration looks like this (the dotted line):

enter image description here
NASA

Call it a ballpark of 7 ft/sec2 (2 m/s2). That graph was from a testbed 737-100 (old jetliner), but the thrust/weight ratio for a jetliner has been around the same 0.3 since.

It's also very complicated to sense and compare in real time to the point that as of writing this the in development takeoff monitor systems will check only the slow-speed segment.

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  • $\begingroup$ 8 ft/s^2 corresponds to a zero-to-sixty-mph time of 11.0 s. (11.4 s to 100 km/h.) 7 ft/sec^2 corresponds to a zero-to-sixty-mph of 12.6 s (13.0 s to 100 km/h). I drive a Mazda Miata (MX-5) that allegedly was capable of doing zero-to-sixty in 8.1 s when new. So my car when new could accelerate faster than a typical takeoff of a 737-100. $\endgroup$
    – rclocher3
    Feb 28 at 21:06
  • $\begingroup$ @rclocher3: Yeah, that's about right. The video in the accepted answer shows how a business jet (also similar T/W ratio) finished 6th out of 7. $\endgroup$
    – user14897
    Mar 1 at 9:03
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Important to include units:

a = F/m

1 Newton = 1 kg m/s$^2$

Mass: 350,000 lbs MTOW × 1 kg/2.2 lbs = 159,091 kg

    189,750 lbs OEW × 1 kg/2.2 lbs =  86,250 kg

Thrust: 2 × 270 kNewton × 1000 Newtons/kNewton = 540,000 Newtons

a = 540,000 Newtons/159,091 kg = 3.39 m/s$^2$ at MTOW

It would be understandable not to use full throttle if the plane was empty.

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  • $\begingroup$ One ton is 0.907 metric tons $\endgroup$ Feb 25 at 6:35
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    $\begingroup$ I've flown a CRJ200 doing touch and goes in a VFR circuit/pattern, with no interior, not even insulation, no paint, and some middling fuel load, not using flex, and the acceleration was... brisk. And noisy. Quite a thrill. $\endgroup$
    – John K
    Feb 25 at 15:24

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