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Week of 4/2/01:
This week's question was submitted by Ron Laird!
Q:
A Boeing 737 and a Beech 1900 are both descending into Cleveland
Hopkins International Airport. The National Weather Service forecasts
light to moderate icing in clouds and precipitation in the
vicinity of Cleveland. The B737 is the first aircraft to descend
into Hopkins and reports no icing. The 1900 descends into Hopkins
next and reports that they are picking up light to moderate icing. The
1900 pilot asks the controller if he has any pilot reports about icing
from other aircraft descending into Hopkins. The controller reports that
the B737 ahead has experienced no icing. Is the B737 pilot mistaken, or is
there another explanation for this apparent contradiction in experiences?
A:
Severity of icing depends on many factors. One obvious factor is the
amount of time spent in icing conditions. It is entirely possible the
737 descended through the icing much more quickly than the light
aircraft. Severity of icing is also "in the eye of the beholder".
What's light icing to a heavy aircraft may be heavy icing for a light
aircraft. It all depends on how much icing accumulation your aircraft
can tolerate.
Congratulations to Norm Worthen.
Although the atmospheric conditions for the two descents are identical,
the airplanes and approach speeds may differ. In some circumstances, the
higher speed of the 737 may be less conducive for ice formation.
A higher speed approach also has slightly higher stagnation temperatures
on the leading edges of the airplane (by a degree or two) and may sometimes
make the difference in the physical state of water. Ron (who flies
757/767s) says, "That's why, as a pilot, you need to take into account
the type of airplane that reports the icing, just as a report of severe
turbulence by a Cessna 152 probably wouldn't concern me too much in
a B767."
-The Aeroquiz Editor
Week of 4/9/01:
Q:
Famed aviator Charles Lindbergh, in addition to his aeronautical prowess
and accomplishments, was an inventor of no small repute. In the 1930s,
after his historical 1927 solo flight across the Atlantic, Lindbergh
a) Built an innovative evaporator that led to the first household
refrigerator
b) Joined with George Eastman and designed photographic
film on a flexible roll
c) Combined several chemicals and created polymer fibers
later known as "nylon"
d) Pioneered interstellar warp drive propulsion, but was squashed
by big oil
companies and their interest in the status quo
e) Developed a precursor to the modern artificial heart
A:
The answer is e). Lindbergh developed several pumps for French
surgeon Alexis Carrel, who was experimenting with keeping organs
alive outside the body. Lindbergh's devices pumped the fluids
necessary to sustain the organs.
Congratulations to Alan Nies.
After a friend suffered heart trouble, Lindbergh joined with the
Nobel Prize-winning Carrel, a surgeon who had ideas of operating
on hearts while the patient's blood was being pumped externally.
Lindbergh produced a series of pumps, the last of which seemed to
work, but World War II began and both men walked away from
the technology.
-The Aeroquiz Editor
Week of 4/16/01:
Q:
One measure of merit used to evaluate sports cars is performance on
a skidpad. This "gee rating" is the maximum lateral acceleration that
a vehicle can sustain during two complete laps around a 300-foot-diameter
skidpad. The new Corvette Z06, for example, pulls a tendon-popping 1.00 g
on the 300 foot skidpad. Impressive as the new 'Vette is, in the
world of aircaft, a hard turn can sometimes require a "skidpad"
the size of Indiana. Why?
A:
Centripetal acceleration. To keep the passengers alive, they must turn
with a sufficient turning radius to prevent excess acceleration from
inducing unconciousness or death. For the NASP test vehicle, the radius
for the 3-gee Mach 12 turn was almost 300 miles.
Congratulations to Chris Snyder.
The radius of your turn is equal to the square of your velocity divided by
the acceleration you want to put you and your airplane through to do it.
When you're flying, say, an SR-71 at better than Mach 3, a turn can
cover a lot of real estate.
-The Aeroquiz Editor
Week of 4/23/01:
Q:
One of the differences in design philosophies used in modern
commercial passenger jets is the use of so-called "gee-limiting"
control systems. Airbus incorporates avionic control systems on many
of their aircraft that limit the movement of the aerodynamic control
surfaces, thereby preventing the pilot from overstressing the airframe
during flight maneuvers. Many pilots object to these avionics. One common
complaint is "I'll risk overstressing the airframe to avoid flying into
a mountain!" However, in some cases, the gee-limiting Envelope Protection
Systems often give greater overall maneuvering performance than
unlimited aircraft. How can that be?
A:
On aircraft without the gee limiting avionics, the pilot
doesn't know when he is approaching the limit, so overall
he tends to stay away from the maximum gee loads. Whereas
on an aircraft with the gee limited avionics, the pilot
knows exactly how far to push it and so takes it to the
limit and hence will get overall better maneuvering
performance. During a class I took on fracture and
fatigue, an aircraft designer from industry told me that
they tried gee limited avionics on fighter jets to try to
reduce the average peak stress the aircraft was
experiencing. They found that the "hot dog" pilots would
push the aircraft right to the limit every time and so
their average peak stress was much higher than when the
pilots had to go on their feel for where the limit was.
They took this feature off the aircraft.
Congratulations to Kelly McEntire.
The Air Line Pilots Association conducted tests comparing aircraft
performance with and without Envelope Protection Systems. One of the
conclusions was that when pilots flew a fully-protected Airbus aircraft,
they attained that aircraft's maximum gee parameters much more quickly
than when flying a nonprotected aircraft. Pilots were more conservative
and slower in their control inputs when flying nonprotected aircraft
and were slower to attain the desired gee loading. Many pilots in the
Association, however, feel that the appropriate solution lies between
the two approaches. One system has been suggested that uses a protection
system, but can then be overridden in preselected increments in commanded
gees at the push of a button.
-The Aeroquiz Editor
Week of 4/30/01:
Q:
"Now this lovely couch," droned the antique furniture salesman,
"is quite unique. It is absolutely form-fitting -- a plaster cast
was made for its occupant and the charming fiberglass shell you see
here was crafted and contoured for his specific shape. A tasteful
crushable honeycomb material is bonded to it and it is lined with
an elegant padding."
"Sounds like 'the occupant' was a real couch
potato," remarked the customer.
"Oh no, sir, quite the contrary.
The people who used these couches were among the fittest on earth."
What is he selling?
A:
It's a chair fabricated for space travel. The fitness of the user
is required to be at peak before liftoff.
Congratulations to Vern Newsome.
Each of NASA's early astronauts had support couches constructed
that were contoured to their specific shapes. These couches were
designed to evenly support body loads during all phases of flight and to
protect from the acceleration forces of launch and reentry.
During the Mercury Program's development, NASA was concerned over
predictions that the ballistic capsule, after separation from the
Atlas booster, in some emergency situations would be subjected to
over 18 gees of deceleration from atmospheric drag. Navy Lt Carter
Collins had, at that point, ridden 12 gees in a centrifuge.
The day after learning of the need for higher gee testing, he rode
the centrifuge in 2 gee increments: 14, 16, 18, and 20 gees!
Collins sustained no injuries, and in fact he walked out of the
centrifuge and later drove home, despite some nausea caused by
inner ear stress.
-The Aeroquiz Editor
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