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Multidisciplinary
Design, Analysis, and
Optimization Branch
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EDUCATIONAL ACTIVITIES: THE NASA AEROQUIZ
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Week of 12/1/97:
Q:
During high-speed maneuvers in modern fighter aircraft, pilots can
experience centrifugal forces equivalent to many times the force of gravity.
When this happens, blood can pool in the body's lower extremities, and the
pilot is susceptable to blacking out. A G-suit counters much of this problem by
squeezing the pilot with expandable bladders to keep more blood in the upper
body. The U.S. Navy's Blue Angels pilots, however, choose not to wear them.
Why?
A:
Two reasons:
1. They don't make the g-suits in the color blue that the
Blue Angels wear (just OD green).
2. They have a strict workout regimen to increase their g-tolerance --
most of their shows do not have sustained g's in
excess of 5 g's, although there are some maneuvers with
instantaneous g-loadings of 8 or more.
Congratulations to Michael L. Jensen.
The suits are restricting and uncomfortable, preventing the Angels pilots
from performing precision flying. Instead, as Michael said, they keep in
excellent shape with rigorous training. When gee forces hit, they squeeze
their abdominal muscles for all they're worth.
- The Aeroquiz Editor.
Week of 12/8/97:
Q:
The carburetion of the British Spitfire and Hurricane fighters momentarily
failed during sudden dives, when centrifugal force interrupted the fuel flow
to the engines. During the Battle of Britain, German Me-109 pilots took
advantage of this problem and performed sudden dives to evade their attackers.
Why were the Me-109s immune to this problem?
A:
They had fuel injected engines.
Congratulations to Anthony lee.
Week of 12/15/97:
Q:
If the engine fails in flight in a conventional (fixed-wing) aircraft, the
pilot can trade altitude for forward velocity and lift and try to find a safe
place to land. The airplane's glide slope depends mostly on its engine-out
aerodynamics. If the engine fails in a helicopter (rotary-wing) aircraft,
is there anything the pilot can do at all to avoid falling like a rock?
A:
The answer is - autorotation, humorously referred to in some
aviation literature as "an exercise designed to keep a
pilot's hands and feet busy while he plunges violently
to his death." If I remember correctly, the rotor is set to flat pitch
(to maintain rotor momentum/speed), then when reaching an
altitude of approximately 50 feet, the pilot pulls back on the
collective and trades rotor momentum for lift.
Congratulations to Dan Shedd.
The main rotor is usually connected to the engine via a centrifugal clutch,
which will disengage if power is interrupted. The main rotor is then able
to free wheel in emergency situations even if the engine or transmission has
seized. The blades have a built-in "twist" from their tips to their roots, one
reason being so that even when the collective is set to flat pitch, the
rotor system is able to maintain its spin as air flows through it as the
aircraft descends. Additional weights are often added to the blade tips to
increase the rotor system inertia so that when the pilot pulls back on the
collective for landing, more momentum is available to trade for lift. If
there is no other damage to the aircraft, if there is enough time to react,
if the weather and landing areas are good, and if it's executed well, an
autorotation landing can be relatively soft.
- The Aeroquiz Editor
Week of 12/22/97:
Q:
In the second Aeroquiz question (Click here
to see it), we wrote that the first sonic boom created
by humans did not occur when Chuck Yeager broke the sound barrier in the Bell
X-1 rocket plane. Instead, the first booms made by humans likely occurred when
the first whips were "cracked" (The tip of a whip exceeds the local speed
of sound and a small sonic boom is created.). What may have been the first
sonic booms created by any living animal on Earth?
No correct answers. The question stands one more week.
Week of 12/29/97:
Q:
In the second Aeroquiz question (Click here
to see it), we wrote that the first sonic boom created
by humans did not occur when Chuck Yeager broke the sound barrier in the Bell
X-1 rocket plane. Instead, the first booms made by humans likely occurred when
the first whips were "cracked" (The tip of a whip exceeds the local speed
of sound and a small sonic boom is created.). What may have been the first
sonic booms created by any living animal on Earth?
A:
I believe that current thinking shows some dinosaurs may have been able to
shake their tails that quickly.
Congratulations to Dennis Thompson.
According to computer simulations performed by Nathan Myhrvold of Microsoft
and Philip Currie of the Royal Tyrrell Museum of Paleontology, the first sonic
booms may have been created by large sauropod dinosaurs like the Diplodocus.
These behemoths could have flicked the tips of their huge tails to supersonic
speeds.
- The Aeroquiz Editor
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