Black asked in Cars & TransportationAircraft · 10 months ago

# Airplane acceleration, how fast?

It seems when you're travelling on an aircraft, either a jet or a turboprop, the acceleration doesn't feel that great. Large or small jets seem to need the entire length of the runway to get in the air. Turboprops can get up quicker, but they still don't feel very fast either. Are aircraft limited to a certain level of acceleration to keep the passengers comfortable, or are they actually going at their fastest possible acceleration at takeoff?

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• 10 months ago

First, let's dispel the notion that airplane 'seem to need the entire length of the runway' that is just plain wrong. Aircraft rarely use more than half of the runway, simply because they have to retain the capability to abort takeoff in case of engine failure or other no-go condition. Aircraft need to accelerate until the decision speed V1 after which they are committed to get in the air even with the loss of power on one engine because they will be in the air with less runway than it would take to stop. If anything happens before V1, then the aircraft is to stop in whatever is left of the runway.

The point is that, if the conditions (wind, temperature, etc) and weight of the airplane are such that it would not be able to perform a rejected take-off from V1 on the runway, the plane is NOT AUTHORIZED to fly.

Now, aircraft could take off using maximum take-off thrust, and they would if required. The max take-off power is a regime that can be sustained only for a limited time, usually a maximum of 300 seconds, since it wears down engine components.

But if the runway is long enough, the conditions are favorable, aircrew are allowed to use an assumed temperature that is higher than the actual. A higher temperature would reduce the thrust setting that correspond to max take-off, which would then reduce engine wear, reduce fuel consumption and noise. If that is the selected strategy, the calculations of V1, Vr  and V2 are done using this assumed temperature so that operation from the assigned runway can still experience a full accelerate stop in the allowed runway length.

The comfort of the passengers is never a consideration, since any jetliner would have a thrust to weight in the order of 0.3 (max takeoff weight, max take off power). 0.3 G horizontal acceleration is not even uncomfortable since, when combined with the vertical acceleration of gravity, it results into an overall acceleration of 1.044 G, the resulting sensation is essentially the same as being on a tilted chair and leaning back.

Source(s): Aerospace engineer
• Anonymous
9 months ago

You need to visit an airport and WATCH them take off and land from an observation deck.

What you think that you feel is highly unimportant.

• 9 months ago

Aircrafts usually takes off at around 82-90% of the throttle which doesnt need full power to take off because overtime the speed increases rapidly among lift, comfort is not about the speed really its mostly about the volume of the aircraft

• ?
Lv 7
9 months ago

0-60 times for planes are generally slower than fast cars due to their weight . A fighter jet might just equal a super car , say 3 sec, after that it’s no contest.

From personal experience I would guess an airliner 0-60 would equal a family car, 10 sec but would equal a super car to 120.

Take off speed in generally around 150-200 and thus is generally achieved half way. Along the runway. Watch top gear, they can’t get supercars past about 180 on a full runway.

• Todd
Lv 7
9 months ago

An aircraft doesn't have to go that fast to get airborne. A large part of slow acceleration in general is more for the safety of the aircraft than the comfort of the passengers. Passenger planes, though already over designed with crazy safety factors, still need to minimize stress to prevent failure due to long term fatigue.

• Zack
Lv 7
9 months ago

Airliners accelerate as fast as they need to for takeoff. Accelerating any faster than necessary wastes fuel and wears down the engines faster. The following determines how fast they will need to accelerate:

1. Type of plane (different planes have different takeoff speeds).

2. Runway length

3. Temperature of the air (different temperature = different air density)

4. Elevation

5. If there's a headwind or tailwind, and how fast it's going (headwind = slower takeoff speed required, tailwind = faster takeoff speed required).

6. How much the plane is loaded (plane is loaded more = higher takeoff speed).

• 10 months ago

They don't always take off at the fastest possible. It is not the most fuel-efficient, and they actually do accelerate pretty quick if you think about how heavy they are.

Jet engines need to spool up to high RPM to start developing maximum thrust. Thrust also improves as ground speed increases because the jet moves forward into a greater quantity of air. Instead of holding the brakes while the jet engine spools up to high RPM, many pilots just allow the thrust generated during spool-up to accelerate the plane. Some airports like SNA (John Wayne, Orange County) have shorter runways so the pilots DO hold the brakes while they spool up the jets. That makes for a faster takeoff.

• 10 months ago

Why would they need to accelerate faster?  If they reach the proper speed to rotate for take off they have accelerated just fine!  Does getting to that speed faster get you to your destination faster? (NO it doesn't). So why would they need to make the acceleration to rotation speed faster?  Runways used by airlines are setup to handle the aircraft that services that airport. They aren't using aircraft carriers!

• FanMan
Lv 5
10 months ago

They  don't need to accelerate any faster.  To do so, they'd need bigger engines, which use more fuel, and weigh more, which uses more fuel, and to carry more fuel on a long flight requires more fuel, etc... so they're designed  to be  just powerful enough and no more.

But STOL planes that NEED to accelerate  fast have big engines to do so, and live with the short flights.