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How may a normal airplane, in flight, become invisible to RADAR?

barker111

This site explains how STEALTH works:

http://www.lowobservable.com/howitworks.htm

 Jul 19 05, 9:15 AM

That's good but this is just a "normal" airplane. No gizmos or gadgets, no stealth technology. It's possible, but how? And having it fly behind a bigger plane, or some such, is NOT the answer.

 Jul 19 05, 9:23 AM
SOTHC

One of two ways, the first being that the plane hedge hops and flies at a low altitude that is below the range of the radar. The other relies on a power failure of the radar equipment and would be a stroke of luck and could not be relied upon

 Jul 19 05, 9:28 AM
skypilot024

Another way would be to drop a load of chaff nearby. The RADAR screen would light up and the airplane would essentially disappear. Controllers really don't like it when that happens.

 Jul 19 05, 5:58 PM

These are good but there is yet another way. It requires the pilot to know the parameters of the RADAR tracking him and some basic algebra. Any guesses as to what he does?

 Jul 20 05, 5:47 AM

Time to kill this off. If the RADAR has an unvarying pulse repetition rate and the pilot knows what it is, he can fly directly at the RADAR at the correct blind speed.
Radar blind speeds occur because of the relationship between the transmitted pulse repetition rate (PRR) and the received pulse-repetition rate. The Doppler pulse repetition rate is the difference between the transmitted and received pulse repetition rates. For example, when the object is stationary with respect to the radar site, the reflected PRR is the same as the transmitted PRR and therefore a net zero signal is indicated for the radial component of velocity. If it happens that the Doppler PRR is the same as the transmitted PRR, i.e., the illuminating PRR, or it is a multiple of the transmitted PRR, a zero signal is also obtained and hence the radar is blind to these speeds, one for each multiple of the transmitted pulse repetition rate. It is not the absolute magnitude of the speed of the object that is measured, but only the radial component of the speed. The radial components of blind speeds, vm , are given by vm = m l f /102, where v is the blind speed in knots, m is the multiple of the radar pulse repetition rate and the number of the blind speed, namely a positive integer, 1, 2, 3, 4, . . ., for the first, second, third, fourth, and so on, blind speed, l is the wavelength of the illuminating radar in centimeters; f is the transmitter pulse repetition rate in pps (pulses per second); and the 102 is a units conversion factor.

 Aug 03 05, 5:46 AM

 What was the first flight instrument ever used in an airplane?

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