You can’t feel speed with your tactile sense, but objects flashing past in your peripheral vision create a strong sensation of fast motion. It dissipates gradually as you get accustomed to it, so that when you’re coming to the stoplight at the end of the exit ramp 45 mph “feels” really slow.
I’m late to the party but I think I can address what the OP is asking about.
The short answer is: climb (or quiet) power.
The long answer:
When a jet (for our purposes let’s just say a typical airliner like a 737) prepares to take off from a runway there are multiple calculations done. The length of the runway, the pressure altitude of the airport, the temperature, the weight of the airplane and the wind are all considerations. Any obstacles on departure (radio towers or hills/mountains) also come into play.
In the old days a flight engineer with a bunch of spaghetti charts would figure out the thrust setting, takeoff roll distance, climb rate and decision speeds. Now this is all done by computers - either on the aircraft or in operations and then the numbers are sent to the aircraft. What you come up with are the thrust settings and speeds required to take off from that runway. This includes a Takeoff Power setting.
Jet engines are like any other mechanical things - the more you run them at their limits, the more likely they are to fail. They are also VERY expensive. So operators want to minimize the time the engines run at very high power settings.
For takeoff you will have a power setting that you must use to get you airborne and satisfy the initial climb requirements. Once airborne and climbing away you can safely reduce power to what is normally called “climb power”. This is a power setting that allows you to keep climbing but significantly reduces the stress on the engines.
The typical climb profile has climb power being set at 1000 feet above the airport you just took off from.
So when you are barreling down the runway you are feeling the acceleration under Takeoff Power. After safely airborne with the landing gear up the power will be reduced to Climb Power. The reduction in acceleration is what you feel as “slowing down”. You are not actually slowing down, but your rate of acceleration is.
The reason it is so pronounced is because the reduction from Takeoff Power to Climb Power is substantial and the airplane is still climbing - all of the lost “oomph” comes from the forward vector. When the airplane reaches climb speed (250 knots below 10,000 feet) Climb Power will still be set and the rate of climb will increase, resulting in almost no feeling in the cabin.
For those of you who want to see this in action - make sure to be listening to the engines right after takeoff. On widebody jets like the 767 or 777 you will be able to hear the power reduction better if you are sitting in front of the engines (ie in front of the wing). On smaller jets with smaller engines (737, MD-80, A320) your best bet is to be in front of and close to the engines.
Also, Merkwurdigliebe was pretty much spot on!
That’s assuming a perfectly flat road. If you’re in a street luge, you’re going to feel the bumps and it doesn’t have the same shocks and suspension system as a car.
Right… and what you’re feeling is upward/downward/sideways acceleration.
The 250kts below 10,000’ limit is mostly due to the need to “see and avoid” other aircraft - including small ones. Wake turbulence is actually less at high speed - the important component of this is the wingtip vortices, whose energy is proportional to the inverse square of the airspeed (and thus insignificant at 500 kts).
Gee, it’s too bad we can’t use a treadmill to test these various explanations… [d&r]
It would never get off the ground, silly. :smack:
As good as all these responses have been, I think they’re all moot except for the illusion ones. That’s all it is, your senses, sight & hearing mostly, are being tricked into thinking your slowing down.
Aircraft create a rather unique set of circumstances at takeoff. Your eyes go from seeing things go by faster and faster and really faster then all of a sudden they seem to be barely moving due to them all suddenly getting farther and farther away from you as the plane climbs. This, combined with your ears going from hearing the roar of the engines and the wheels rolling faster and faster over the runway to, again, very suddenly them getting much quieter with the wheels not being in contact with the runway and a great deal of the engine noise suddenly not being reflected back to you from the runway.
The first few times I took off in a jet, looking out the window I was sure we had suddenly stalled and were about to drop like a stone!
Engine power is only half of what governs airspeed. Pretty much ignored in this discussion is that the aircrafts rate of climb limits it’s speed.
We all realize that hills effect our speed when driving a car as much as the throttle. Aircraft have the ability to climb and dive at will, in essence creating thier own hills.
Shortly after takeoff, the aircraft will establish an airspeed associated with one of:
-best rate of climb (usually optimal for fuel efficiency)
-steepest angle of climb (good for terrain avoidance or noise considerations)
-a shallower angle that gives higher speed, and thus more distance covered in-route.