PHILIP GREENSPUN:
Quick introduction. I know hardly anybody says
they care about helicopters. But as God is my witness,
I'm going to change that. If I can reach one of you
airplane obsessed folks, I will do my best. So what is cool
about a helicopter? Here, it's the view. So let's start, first and
foremost, it's a view. So these are some
pictures that I snapped on a trip from
the Robinson factory in Los Angeles back to Boston. Who recognizes the
city in the middle? Ooh, some Midwesterners
here, Chicago indeed. Of course this is the Stata
Center where we'll be tomorrow, remember that, 32 141. What are the parts
of the helicopter? If you're between
ages 3 and 5, it's acceptable to call it the
thing on the top the propeller but older than that, it's
better to say main rotor system. Tail rotor is in
the back-- we'll talk about why we
need that in a minute. You got to have transmissions. In helicopters, the
speed of the engine is never the speed that
you want, I don't think. And landing gear
is kind of nice. Although for
record-setting flights, sometimes people
have taken them off to try to get a little
higher a little faster, and then they just
land very gently. So your typical
helicopter drive train will have transmissions
for both the main rotor, and they'll have
another transmission to adjust the speed of the
tail, maybe gear it back up a little bit. This unfortunately does
introduce another source of unreliability. So in the airplane,
you've got your engine, it's bolted to the propeller. As long as the engine's turning,
it's hard to have a problem. The propellers don't generally
just come apart in flight. But here with the
helicopter, you might have a working
engine and working main rotor and the transmission,
all the oil might come out and the gears seize up. There's a couple of warning
lights in there for when you're having a transmission problem. This is the rubber
belt system that's used in some piston helicopters. I think this is probably a
drawing off of a Robinson. But basically, you have
pulleys on the engine side and on the drive change side,
and you have these rubber belts connecting them. So you can start your
engine with the belts loose and then tighten
them up when you want the engine to begin
driving the rotor system, that way you don't have to
have the little starter motor actually turn all
the rotors and stuff. How does it work? So Tina is a hard act to follow
with my cave person computer programmers
understanding of lift. But if you assume that the lift
is a combination of Newton's third law and the Bernoulli
principle, the sped up air has more kinetic
energy, therefore for conservation
of energy, it has to have less of
something else, it's going to have lower
static pressure. So here's one of the
FAs diagrams here. We have velocity and
pressure that are equal. They go into the Venturi. The velocity is higher,
the pressure is lower, so the energy of the
air is still the same. And it comes out again at the
same velocity and pressure. So you're getting
lift from the wing from both Newton's
third law just pushing air down
makes the wing go up and the Bernoulli principle of
generating some low pressure. This is the same drawing
you saw earlier of how when you exceed a certain
critical angle of attack, depending on the
air foil, your lift party comes to a quick end. It doesn't go away completely,
but it's a sudden drop. Angle of attack, so remember
there's your cord line, there's your relative wind,
4 degree angle of attack and a reasonable amount
of forward speed. Remember the lift varies
is the speed squared will have you going. And if you want to
fly slowly, you just go to higher and higher
angles of attack. So why not hover
in your Cessna 172 and save yourself the trouble
of getting a helicopter rating? It's because you know
off the right end of this chart you quickly get
to the stalling angle of attack and the plane
doesn't fly anymore. So there's an FA drawing I
think from the pilots handbook where the airflow becomes
turbulent somewhere between 12 and 16 degrees angle of attack,
depending on the air foil. And that's why the
Cessna can't be used for hovering operations. What if you saw the wing off
the Cessna and spin it around? So if you do that,
the wing will always have airspeed even if the
fuselage is not moving. And that was an
idea that was first reduced to practice in 1907. So only four years after
the Wright brothers flew, a couple of guys in
France were actually hovering a little bit
in the helicopter. The first helicopters that
could be flown and controlled and actually operated as
a practical aircraft I think mid 30s in Germany. And then Sikorsky is famous
for being the first mass producer of helicopters
with the Sikorsky R-4. It was used for a few
computational purposes in World War II, search
and rescue type stuff. But really, the Korean
War was the first time that helicopters were
widely used by the military. Let's talk about a very simple
qualitative physics here. We're spending on the ramp. So we spin the rotor
system up to 400 RPM. But we're still on the ramp. So does anybody have
a brilliant idea for how do we get up into
the air where we want to be? AUDIENCE: [INAUDIBLE]
were negative, because there [INAUDIBLE]
of the main rotor system. PHILIP GREENSPUN: OK, excellent. So-- what's your name? Sorry. AUDIENCE: Aziz. PHILIP GREENSPUN: Aziz
has a correct observation that if you want to get
the same lift out of a wing without changing the speed,
we don't want to have this-- we don't want to speed up too
much because the tips will go supersonic, and the neighbors
will begin to complain. So we just twist the
blades up a little bit. And as they're twisted
up, they'll bite more air, generate more lift,
and the helicopter will begin rising up. What will happen to the speed? Let's hear from one of these
aeroengineering heroes. As we generate more
lift, what happens? AUDIENCE: You now have
more drag on the rotors, so the engine slows down. PHILIP GREENSPUN:
More lift, more drag, so without adding more
power, the engine-- well, without adding more power,
the blades will slow down. So you want a correlator. As you're lifting the collective
control on a helicopter, the correlator is
opening the throttle and adding more
power automatically. And there's also an
electronic governors that will just touch that up a
little bit by watching the RPM. Turbine helicopters
all have governors. Most piston-- Robinsons
have governors, as well. All right, so what if
we're parked on ice? Has anybody here seen
my favorite movie, Blades of Glory? So when Will Ferrell
and his partner, what if they're on the ice
and they push each other? What happens? Both go backwards, the
pusher and the pushee. So keeping in mind Blades of
Glory, an important physics work, what if we're
parked on the ice? What happens to our helicopter
after we start the engine and start the blades spinning? AUDIENCE: [INAUDIBLE] PHILIP GREENSPUN: Helicopter
spins the other way, excellent. Yeah, so that's Newton's
third law, once again. For every action, there's an
equal and opposite reaction. You're not going to see that
as dramatically if you're parked on pavement,
because of the friction. So what do we do? We add the tail rotor. So here are the forces up here. There's the blade rotation. There's the torque. To counteract the torque,
we've got the tail rotor thrust to blow the tail
back into position. And the only thing here that's
not corrected, you'll notice, is the tail rotor thrust. So if you set
everything up the way you would think obvious, like
put the rotor mast straight up and put the tail rotor on
it, the whole helicopter with the controls neutral
would drift to the right from the tail rotor thrust. Because it's pushing the tail. The helicopter wants
to rotate that way. The tail rotor blows
it back this way. And that would blow
the whole machine off the side of the
ramp if the pilot didn't hold a lot of left cyclic. So to counteract
that, the helicopters are rigged with the mast
at a slight left angle so that they don't
have this tendency to go off to the right. AUDIENCE: [INAUDIBLE] question,
what does the governor do? PHILIP GREENSPUN: The governor,
yes, let me reinforce that. So yes, as you
generate lift, you get more drag, which will
cause the blades to slow down. So there's a
mechanical correlation. As you're raising
the collective, the throttle's being opened
just kind of blindly. And the governor is
touching that up. The governor is
watching and maybe twisting the throttle
control slightly to fine-tune the throttle
to keep the blades exactly at 400 RPM. Let's say that's
the [INAUDIBLE].. For a pilot, pilots are-- you don't want to distract
the pilot too much, so the gauge is just
calibrated in percent. It's 100% RPM. That's good. That's all you need to
know about your helicopter. I think in the
Robinson, it works out to pretty close to 400 RPM. All right, forward flight-- so we're hovering and
we want to go forward. So it seems obvious that
we want to tilt the fan. We want to push the
fan down this way, and that way, we'll get some
horizontal vector of thrust and we'll be going forward. But where do we push it from? It's a spinning gyro, so
it has a lot of stability. If we're really strong and we
reach up from our pilot seat and try to nudge
the rotor system, why wouldn't that just cause
the helicopter fuselage to move underneath the
fixed rotor system, instead of moving
the rotor system? There's nothing to fix unless
we can call up an incredibly strong friend,
and say, would you mind holding the helicopter
in a fixed position? We don't have anything
to push against in order to tilt the rotor. Does that make sense? You've got this gyro on top
of you, and disturbing it is going to take a lot of power. And even if you
had the strength, you don't have anywhere
to stand rigidly and push. So what do you think? Could the rotor just fly
itself into a new position? And how would that work? How could you use
the spinning wing itself to fly itself into
a new tilted-down position? Anybody have any
brilliant ideas? AUDIENCE: You increase
the angle of attack of the blades on one
side [INAUDIBLE].. PHILIP GREENSPUN:
What's your name, sorry? AUDIENCE: John. PHILIP GREENSPUN:
John has a good idea. So John says, increase
the angle of attack and decrease it as the
blade moves around the disk. So if you can increase the
lift on part of the disk compared to another
part of the disk, it will naturally tilt itself. So if you want to
go forward-- let's ignore gyroscopic
procession for a moment, because I think we've proven
that nobody understands it. Let's just say that we could
make the angle of attack higher on the back of the
disk compared to the front. Then the back of the disk
would have more lift. It would rise up and the
front would go lower, and then you would see this
flight path that you do see. That make sense? So basically, you're basically
flying the rotor system. You're not flying
the helicopter. The helicopter's just hanging
from the rotor system. That's a good mental model. And all of the power is from
the engine to the rotor system. So that's a natural
place to do it, just by tweaking the blade
angle as it rotates around. So the left hand is collective,
moving the blade's angle regardless of where
they are on the disk, and the cyclic, which
is changing the pitch cyclically as you suggested. All right, what's the magic? This design-- I'm
not sure it's really changed at all since the
very first helicopters. Maybe those brothers in Paris
didn't have one in 1907, but I'm pretty sure that
every helicopter since then has had this. There's a swashplate. Watch this-- so the lower
part of the swashplate here is fixed and connected
to the flight controls. And then there's a bearing,
and the upper swashplate rotates with the blades. Does that make sense? So if you lift the
lower swashplate up, that pushes the
upper swashplate up, which pushes these
rods that are connected to a corner of the blade. And that'll cause the blades
to tilt. That make sense? So you have this
rotating swashplate that's connected to a
corner of the blade. And if you push
the whole thing up by yanking up on the
collective, then you can see the blades
actually twist. You can do that in the hangar
and see the effect of this. At the same time, in your
right hand is the cyclic. And with the cyclic, you're
tilting the swashplate. So with the tilted
swashplate, that will just cause the
blades to twist up and twist down as they rotate. So it's a pretty
elegant solution. This is not carrying much of
the load of the helicopter. There's still a mast
holding the whole thing up. This really just has
to carry enough force to twist the blades up and
down, up and down, up and down. So that's your
engineering design. Everybody appreciates that? Do we want to take off straight
up like in a Hollywood movie? Well, if you have one or two
people in a helicopter designed for four or five,
you actually do have enough power to do that. However, there is
something over here on the right called the
"height velocity diagram." And you can see it says, "avoid
operation in shaded areas." So they're saying-- we'll
talk about this maybe a little later if people are interested. But if you are, let's say, up
at 200 feet at zero airspeed, so you're just parked, hovering
200 feet above the ground, you don't have huge stores
of forward speed, which is kinetic energy,
or potential energy, because you're only up 200 feet. So it's going to be hard to
do an auto-rotation that's perfect and doesn't bend
anything, especially because the FAA says, if
you're up high like that and the engine
quits, in test pilot, you have to sit there with
your arms folded for one second and do nothing, because
that's what would probably happen in real life. You'd be surprised. People can do
auto-rotations from 200 feet and land perfectly, but
they know it's coming. They chop the
throttle themselves. They immediately put
the collective down and they do the auto-rotation. So but basically, if you're
a pilot of average skill and you don't do anything
for about a second after the engine
quits, then this is supposed to keep
you safe, by you either fly 50 knots or faster, or you
fly 400 feet or higher at sea level, and higher than
that at high altitude. So what we're actually
recommended to do-- see this recommended
takeoff profile-- is skim along the ground until
we get up to about 45 knots and then let the
helicopter climb. I think this is the
curve for a Robinson R44. Why would you want to do
that, aside from safety? Another good reason
to do that is you watch these drag
versus speed curves, and you see that you
reach kind of a minimum. This is some generic
helicopter from an FAA book. It's actually 55 knots
for the Robinson. But if you can go 55
knots, you need less energy than any other airspeed. So the idea for a takeoff
is you nudge the helicopter forward a little bit. If you can build up
two knots of speed, that gives you excess power. You can use that excess power
to climb up three inches or you can use that excess
power to accelerate, maybe to three or four knots. And if you just
keep accelerating using your extra
power to accelerate, the faster you go, the
less power you need. So even if you've never
touched the collective or drawn any more
horsepower, as long as you have an open
area in front of you, you will accelerate. And once you hit 45 or 55
knots, your hover power turns into significant
excess power that you can use for a climb. So that's why you
often see helicopters at airports taking off kind of
like a short-field airplane, and also landing a bit like
a short-field airplane. Straight and level, it's
very similar to an airplane. The performance is all a
function of the attitude that the aircraft is in. Is it pitched up or down and
how much power is being applied? And that's an indirect function
of the collective position. So as with an
airplane, remember, your pitch controls your speed. And the amount of power-- throttle in the airplane,
collective in the helicopter-- determines whether you're
climbing or descending at that air speed. Your attitude indicator in a
VFR helicopter is the horizon, so you're watching
the horizon carefully. The reason why people who
are instrument-rated airplane pilots, they jump
into the helicopter and they can fly it immediately,
and people who've never flown have a tough time. It takes them 10 hours. And the reason is
that people who are instrument-rated
airplane pilots, they become very
sensitive to watching for small changes in attitude. The anti-torque
pedals-- remember, we had that tail
rotor, and we adjust it so that the tail doesn't
spin around on the ground. In the air, we adjust it
so that the helicopter is streamlined into the wind. We don't actually have to
use them to make turns. There's no adverse yaw
as in some airplanes, where it'll start skidding or-- there's none of
that, or slipping. All we do to make a turn
is we put the helicopter, using the cyclic, into
a little bit of a bank. And then we wait. So if we have, let's
say, a 10-degree bank, the helicopter in one minute
will make a 180-degree turn. Landing with power-- so
again, like an airplane, if you see the
spot in the ground, you adjust the power so
you don't overfly the spot or underfly the spot. If the spot's rising
up in the windshield from your perspective,
that means you're going to land
short, so you add power, raise collective
in the helicopter. If the spot is descending, then
you're overflying the spot, so you have to reduce power. It's a purely visual
maneuver, except when you're landing on a pinnacle. And the reason for that is if
you're landing on a pinnacle, you don't get a sensation
of your forward speed from the ground rushing by. So the idea in the
helicopter is to land, unlike with the airplane. It's actually a little bit less
unnerving than an airplane. Some people get a little bit
ground-shy in the airplane. They're happy flying 80
knots in the pattern, but they're not that
happy flying 70 knots 10 feet above the runway,
which makes sense, because you don't want to slam
into the ground going really fast. The good news is
in the helicopter, you never get to
that phase where you're going fast
close to the ground, because when you're
landing, you just say in my peripheral vision, how
fast is the ground rushing by? And you just kind of
keep that constant. Whatever it was up at 500
feet above the ground, that's what you want when you're
five feet above the ground. And you'll very
naturally slow down. You'll do the right--
your natural instinct to slow down as the
ground begins rushing is a helpful one
in the helicopter. So your peripheral vision
is used for speed reference, and the spot moving up or down
is used for a descent rate reference. And that's why you never have
to look inside at the gauges, except when you're landing
on top of an office building or something. Can you land the
helicopter without power? It turns out the answer is yes. You have these three
buckets of energy that I alluded to earlier-- kinetic from your forward
airspeed, potential from being up high, and then
another form of kinetic, which we'll call "blade inertia"
from the relatively heavy blades spinning. So raise your hand if you
think the forward airspeed is number one in terms of size. Let's rank these. What's the biggest--
airspeed, a heavy helicopter going 100 knots,
potential energy, helicopter having been
lifted up off the ground, or the blades whipping around
near the speed of sound? Who votes for one,
forward airspeed? A few. Who votes for potential? A fair number. Who votes for blade inertia,
the blades whipping around? All right, good. We've got a good distribution. Let me give you-- I'll tell you about, I think
it was a crazy French guy who got into what's now called
a Eurocopter, an Alouette, went up to 40,000 feet to
set an altitude record. The record was set when
the engines flamed out-- that's why it's 40,000 and
change, not 41,000 and change-- and then auto-rotated all
the way down to the ground. So whatever energy
bucket that was there had to be sufficient to make
it all the way the ground. So what does that tell
you the biggest one is? It's got to be something that
scales up to 40,000 feet. Potential, yeah. So potential energy
is a good candidate for the biggest,
because again, you've got to keep the rotors
spinning for longer if you're auto-rotating from 10,000 feet
or 50,000 feet or wherever. I don't think that record's
been broken, actually. It was set in the '70s. So number two is the forward
airspeed of the helicopter. The blade inertia isn't good
for much except for cushioning your fall from five or
10 feet above the ground. So what you do in the helicopter
if the engine were to fail-- number one reason
is fuel starvation from failing to top it off. Helicopters are often short on
payload, so people will say, I want to take these
seven people somewhere, and I'd be overweight
if I fill the fuel tank. So I'll put in half an hour of
fuel for this 15 minute trip. Actually, that would be illegal. 20 minutes is the
minimum reserve. So I'll put in half an hour of
fuel for this 10 minute trip, and then there's a bit of a
delay, and you run out of fuel. There is a warning
light at 10 minutes. And the good news is you can
land in a field, a baseball field, pretty easily. So the engine quits
for whatever reason. Let's say you run out of fuel. You want to get to 60 or 70
knots, some reasonable air speed. And then the
challenge is to hold that airspeed even as the
ground is rushing up at you. You hold it right till
you're at treetop height, about 40 feet above the ground. Then you begin to flare, just
like in an airplane flaring for landing. You scrub off that
forward speed. And that reduces
your descent rate. So you can reduce your
descent rate to zero by bleeding off
all of that energy from the forward airspeed. And the kinetic energy,
remember, is mv squared. So it's very important. There's twice as much energy at
70 knots compared to 50 knots. So once you've scrubbed
off all your descent rate and all your forward
speed, you're like this. So your tail is going to be low. And now you're going to
just fall to the ground and hit the tail first. So it's not going to
be an FAA quality-- you're going to walk
away, but it's not going to be an FAA-quality landing. So what you can do
is stick forward and settle by pulling
up on the collective. So you stick forward
to level the skids. And then when you're about
five feet above the ground or maybe two feet
above the ground, you start pulling
up on the collective to cushion your fall
that last few feet. So you've used up
potential energy keeping the blades windmilling. If you just flatten
the collective, the blades will have a
relatively normal angle of attack to the air that's
now coming from below. You've kept up
your forward speed, and you bleed that
off at the end to reduce your vertical speed. And then finally, you go-- [VIDEO PLAYBACK] The guy cheated. [END PLAYBACK] What's the cheat? And I'm telling you the
cheat is you can hear it. You could hear the
cheating going on. He landed with zero
forward airspeed. Why? What enabled that? And like I said,
you could hear it. AUDIENCE: [INAUDIBLE] PHILIP GREENSPUN: It's not
from the engine running. The engine was
presumably at idle. So what was the cheat? Nobody heard? AUDIENCE: The wind
probably [INAUDIBLE].. PHILIP GREENSPUN:
Wind, exactly, yes. What's your name? AUDIENCE: Messen. Messen. PHILIP GREENSPUN:
Messen figured this out. So basically, he landed
with probably-- it's very hard to kill all
of your vertical speed and all of your forward speed. So if you go out and it's
15 knots down the runway, if you can just get
down to 15 knots, and instead of sliding and going
[MAKES NOISE] down the runway, which is common and not
harmful to the helicopter, you'll have a perfect, what
looks like a perfect landing. It's very hard. In the big helicopters
like a Huey or something, it's practical to do a
zero/zero landing out of an auto all the time. In a Robinson, it can be tough,
but the wind helps hugely. And like I said, the
throttle was down at idle, so the engine is not
really doing anything. Question? AUDIENCE: The tail rotor
was still spinning. Is auto-rotating [INAUDIBLE]? PHILIP GREENSPUN: It is, yes. Great, great question. So there's a sprag clutch,
which prevents the rotor system from trying to drive the
engine, because that would introduce a lot more drag. But the main rotor
and the tail rotor are yoked together, so you
still have tail rotor control. Great question. AUDIENCE: [INAUDIBLE]
directional, because you don't really
need the torque anymore, so-- PHILIP GREENSPUN: Yeah,
you don't need much. I don't know. I'll have to think
about why it's useful. AUDIENCE: [INAUDIBLE] PHILIP GREENSPUN: Yeah,
it's not useful for much. That's for sure. One thing that is good about
it is the hydraulic pump is also geared to
the transmission. So you still have
hydraulic boost even if you're auto-rotating
from super high. What can you do
with a helicopter if you have a private? You can visit schools. I visited the Winchester
Public Schools. I'm not sure you can
give them all rides if you only have a private. There's some kind
of-- like I said, there's those
charity laws that-- regulations that we
don't really worry about, because we have
commercial certificate and a letter of authority
from the [INAUDIBLE].. But here's one of the East
Coast Aero Club helicopters. I flew to the public
schools in Winchester. I gave all the kids rides. And when we flew over
houses like this, I said, oh, that's just like
the house where I grew up. If you do that with kids
from Weston and Lincoln, they believe you. They don't parse that
as an ironic statement. Helicopter pilot careers,
just in case any of you guys are thinking about leaving the
desk where all the people work as a flight
instructor, fly tours in the Grand Canyon or
Alaska, and then they'll either go to offshore oil
or Medevac after that. Usually offshore oil
used to be easier to get. When oil prices are low,
when oil catches a cold, the helicopter industry
catches the flu. They shut down these oil rigs
and there's a lot less need for helicopter transport. Medevac is kind of
considered the plum job. That's my friend, Marcus. He trained at East
Coast Aero Club and now he does 12-hour shifts
at a volunteer fire station. And he gets paid
in North Carolina and goes hospital to hospital,
or sometimes picks people up off of highways and stuff. So what can you do? You can fly low and slow
both legally and safely. You saw there was a
carve-out for helicopters able to fly lower. One problematic aspect of flying
Piper Warriors and Cessnas is that people-- their expectations of what an
aircraft is and what it can do has been set by their
airline experience. And the first time you
try to get up and use the bathroom in
your Piper, you'll discover that JetBlue has some
advantages in the aircraft department. And your passengers
will notice this, too. This is noisy. It's not climate controlled. There's no bathroom. The helicopters are awesome,
because people usually haven't even been
in one, so it's a whole different experience. There's a different view. You can take them on a 10-minute
ride from Hanscom Field and go back. You don't have to
say, oh, let's go have lunch in Martha's Vineyard. You just take them
on a little tour and they say, wow,
this is awesome. So when I actually want to
show people what GA is like and what my world
is like, I usually take them for a helicopter ride. I don't take them for a trip. The serious is for
transportation, and the helicopter
is really what I think of as the
kind of aviation dream that people had
in ancient Greece. They didn't dream of
going to LA in six hours. They dreamed of
soaring like a bird. You can land off-airport. That's where a lot
of the challenge comes from the helicopter. People think you're a
pilot of heroic skill if you take off and
land at Hanscom. That's not very challenging. It's not really that different. And in some ways, it's easier
than taking off and landing in a Piper or a Cessna. When you're
off-airport, you have to exercise a lot of
judgment, a lot of skill. And that's part
of your training. But it's also where
people get in trouble hitting obstacles and stuff. If you do get all of
your airplane skills, you can transfer them over
to helicopters very easily. It's 30 hours minimum
of additional training to add a helicopter rating. 40 is probably a
good budget number. All right. Are there helicopter questions? AUDIENCE: [INAUDIBLE]. Can you just pick [INAUDIBLE]? OK, here it is. Or like, who's going to
tell you [INAUDIBLE]?? PHILIP GREENSPUN: That
is a great question. Is there any
regulation about where you can land your helicopter? The answer is until about 5 or
10 years ago, there wasn't any. So it was just permission
of the property owner and don't do anything
careless or reckless. So basically, the whole world
was open to helicopter pilots. There is a little bit of
a tweaking of the law. The FAA passed this-- they added this
regulation that I think was intended
for airplanes, but they forgot to carve it out. So they said if you make more
than 10 takeoffs and landings in the same place
in a year, then you have to get it approved as
an airport with a huge amount of regulation. I think it was intended for
mining companies that would set up their own landing strip. It doesn't really make sense. For helicopters, like if
you have a construction site that you want to
regularly visit, now it's a bit of a hassle because
that 11th landing, in theory, you need it to get
approval as an airport. But as a first
approximation, you can land anywhere
that the property owner is happy to host you. And towns, also. They're really aggressive
about harassing people who try to have a
helipad at their house now, just because they can. They get them under zoning
laws, even though they're not really supposed to. The FAA is supposed to
have exclusive authority to regulate aviation. Because think about
it-- there's all this-- there's so many levels
of government in the US. If you let them all
just forbid activities, eventually there
would be nothing that was legal at all, because
people in Concord and Lexington would say, we don't want
airplanes flying over our head. So we'll just make it illegal
to fly a Gulfstream in Concord. AUDIENCE: [INAUDIBLE]
from flying [INAUDIBLE]?? PHILIP GREENSPUN: I had
that in an earlier slide on learning to fly. The marginal cost
is about double. So it goes from 150 an
hour to 225, or 100 an hour to 200, because so many rotating
components get discarded after 2,200 hours--
so the transmissions, the blades, and so forth. So it is more
expensive per hour. However, like I also
said, the flights tend to be a lot shorter. So I would say as a
hobby overall, it's about the same cost, because
you're not dragging people all the way to the
Vineyard or Bar Harbor. You're just taking
them into Boston and back out, which is about
20 minutes of flight time and 30 minutes of
engine running time. Whereas an intro airplane flight
would be an all day thing. You'd probably fly a couple
hours, two or three hours. So you actually probably
spend more with the airplane. That's a great question. All right, so I guess we should
take a 10-minute restroom break. And after that, we're going to
hear from Laz about the F-22.
