PARACHUTES have made safe escapes from crippled aircraft a reality鈥攂ut
it鈥檚 not always easy to jump out after a mid-air collision, or after the pilot
has lost control of the plane and gone into a spin. So a company in the US has
decided that it鈥檚 time for stricken planes to be lowered to the ground safely,
using a large parachute attached to the fuselage.
Cirrus Design of Duluth, Minnesota makes the SR20 light aircraft鈥攖he
first plane to have a built-in parachute system to be licensed for sale by the
Federal Aviation Administration. The parachute Cirrus has developed works at
altitudes of less than 300 metres with the aircraft in a full spin. It will
allow the plane to land the right way up鈥攂ut as it comes to earth at 17
miles per hour, it uses the landing gear as an elaborate shock absorber. When it
touches the ground, the undercarriage shoots through the wings鈥攚riting off
the plane but leaving the fuselage and its passengers intact.
The parachute is activated by pulling a lever. A rocket is fired from the
rear of the fuselage to project the chute to a safe distance from the plane
while it is still in its bag.
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鈥淎 normal parachute would then open all at once, which is fine at low
speeds,鈥� says Paul Johnston, chief engineer on the project. But, he says, at
high speeds the load force be so great the parachute would not work. 鈥淭he force
would tear it to shreds.鈥� Either that, or it could be ripped away from the
plane. To avoid this, the parachute uses a cloth slider to control the rate at
which it opens. The slider slithers down the cables, letting air into the canopy
so that the stricken aircraft slows to a safe speed before the parachute can
fully open.
Three straps connect the plane to the parachute, one from the rear and two
from the front part of the fuselage (see Diagram). The two front straps run
along the side of the vehicle and are contained within it, moulded into the
fuselage during manufacture. Once deployed, they are ripped out of their
casings, which are jettisoned.FIG-mg21811301.JPG
Rae Willis of Morristown, New Jersey, has flown light aircraft for 40 years.
He says that pilots are most likely to go into a spin below 300 metres when
turning into their final approach to land. 鈥淭he key is that it鈥檚 a last resort,
which is probably more use at higher altitudes. Yank the handle and cross your
fingers,鈥� he says.
Cirrus has more than 250 advance orders for the plane and expects to deliver
its first parachute-equipped aircraft in early April. But tragedy struck the
company last week when one of the firm鈥檚 test pilots, Scott Anderson, 33, was
killed while flight testing the SR20. He crashed while attempting an emergency
landing. The test aircraft was not fitted with the parachute system鈥攖hough
it鈥檚 unclear if it would have helped in this case.