PHILIP GREENSPUN: All right,
so a complicated aircraft will have a lot of systems. These are the systems from
the Canadair Regional Jet. How well did that I fly it? We landed it once in Toronto,
and I was doing this, and the captain
said to me, well-- he was a young guy-- he said, well, you know nobody
was born knowing how to fly a 53,000-pound jet. But anyway, this is
the kind of stuff you have to learn
for the big aircraft. Here are these
systems that we're going to talk about that you
have on a small aircraft. The engine, first of
all, what are the types? You might remember
the cool old days. You had these big
radio engines, and they went up to 3,500 horsepower,
I think, was the biggest one. But your typical
World War Ii fighter might have a 2000
horsepower-ish radial engine. Turboprops, so we'll
get into this more. I have a special lecture on
turbines and multi-engine. But it's a jet engine that's
hooked into a propeller, and that lets you land
on shorter runways, and it's more fuel-efficient
at lower altitudes. The popular examples,
the Pratt & Whitney PT6 has been around since the 50s. A competitor from the similar
era was designed by Garrett. Those have typically
slugged it out. One of them is a free
turbine, so you have the PT6. And this is a GE Walter
derivative, that they now call the GE Advanced Turboprop. So the cold air comes in. It gets burned. And the hot exhaust
gases spin this power turbine which has a shaft
that drives the compressor. And it also goes back this way. There's a second. I think one of them
drives the compressor, and there's a second
wheel there that is exposed to the hot gases and
it will drive the propeller. So there's kind of a fluid
coupling there through the air. Whereas the Garrett Honeywell
product has a direct drive transmission that's more
complicated but also a little bit more
fuel-efficient. So those are the
two big designs. You get a lot more
reliability with a turboprop if you need power. It's hard to make a piston
engine reliable if it generates a lot of horsepower. The disadvantage is
nobody's really figured out how to make these things
for less than half a million dollars new in a box. And the most popular
airframes for the turboprop for things that you might
fly, the Beechcraft King Air which is twin-engine,
and the Pilatus PC-12 which is a single. Turbojets, which-- well, the
FAA calls them turbojets. They're really turbofans
because of the bypass air. We'll see that in
the next slide. These are-- one thing
to remember about them is they're normally aspirated. They actually do produce
less and less power as you get up to
higher altitudes which is important for taking off, you
know, in Colorado on a hot day. You have much lower
noise and vibration-- maybe not if you mount one
of them right over your ear. That's a Cirrus
jet which is kind of a cool simple personal jet. They actually have sort of
taken over the market starting in model airplanes going all
the way up to the Boeing's and the airbuses. And the only gap where
turbojets have not taken over is in your family
airplane, right? Your four-seater,
your six-seater, that's where
nobody's figured out how to make a
turbojet that really makes economic sense or
even sense for the range. They tend not to be as efficient
at these low-power settings. The smaller the turbojet, the
less efficient it has been, unfortunately. So you wouldn't get
the kind of range that you'd get out of
a Cirrus or a Cessna if you stuck a jet
engine in there. These are more vulnerable. A bird will usually just get
Cuisinarted by a propeller, but if it goes into the jet
engine then it can destroy it. So the single-engine jet,
well, some single-engine jets like fighters they should
have an ejection seat. The Cirrus single-engine
jet has a parachute for the whole aircraft
to float you down. All right, turbojet, again,
this is not really on the exam but it's just good
general knowledge. The fresh air, it comes in here. It gets compressed
by the compressor. Once again, that's
normal aspiration, and so it's just a
fixed-compression ratio. It doesn't get more extreme
like with the turbocharger in a piston engine
at higher altitude. Notice this bypass air. It's being spun, and
that blade in the front is really acting
like a propeller. Here is where the compressed
air gets burned and drives these power turbines
that drive the compressor and the fan in front. So it seems like a
really simple design, but there's a tremendous amount
of engineering in the blades. And if anything is fabricated
just slightly wrong, you know, the whole thing comes
apart and explodes. So that's one reason
I think they're in the million-dollar range for
a typical business jet engine. All right, so let's go
back to our world, which, unfortunately, is going to be
the reciprocating piston engine kind of like in your car. The designs-- I don't know-- the fundamentalists
may or may not have changed that
much since the Wright brothers, but
certainly, the designs that are in your modern
Cessna or a Piper-- the basic geometry,
the engine design-- is really all from the 1950s. The good news is that with
numerically-controlled machine tools and such,
they're much more reliable than they used to be. Engine failure was
an everyday event at a busy airport
in the old days. And now, you know, I've
flown for, I don't know, 4,000-plus hours with Pistons
and have never had any kind of real engine problem. The horizontal opposition
supposedly smooths things out. They may ask you about
that on the test. Like the turbojet, it's
normally aspirated, so the performance
degrades as you go to hot and high elevations
where the air is thinner. We'll talk about that in the
performance calculations. You directly drive
the propeller. So if the engine's
spinning at 2,500 RPM, the propeller's
spinning at 2,500 RPM. There's no transmission. The cooling is the air,
it's called air-cooled. And the air flows
over the cylinders, but there's also a lot of
oil circulating which has a significant cooling function. The lowest cost and
simplest airplanes have a carburetor rather
than fuel injection. And you'll get 200
horsepower or less out of a-- well, I guess the
latest Lycoming's can do to 215 out of a 4-cylinder. You can get a
little bit fancier. A plane like a Cirrus
or the latest Cessnas will have fuel injection. Turbocharging sounds like the
ideal thing for an aircraft. Why wouldn't you want
that for a machine that goes through airs of all
kinds of different densities? It seems like the ideal thing. Just make the density
back to sea level at least all the time, which is
called turbo-normalization. The problem is that
they share an oil system with the rest of the engine, so
when the turbocharger breaks, it tends to cause all of the
oil to leak out of the engine. And now you have a broken-- you know, what had been
a perfectly good engine with a broken turbocharger
becomes a real emergency. So people's-- you know, except
out west where you really need the performance because
you are going up high a lot or you're starting
from high and hot, the turbochargers
tend to be unpopular, although it's an ideal
engineering solution. The more cylinders also
the less vibration, so if you have higher
horsepower or if you just want it to be smooth. Like the original
SR20s came with six-cylinder,
200-horsepower engines because they wanted
it to be smoother. Rotax is the most popular
engine in the light sport and experimental world. That's an engine that's a little
bit more like a car engine. It revs pretty high. It's got a water-cooling
radiator with antifreeze and the transmission gears that
prop down to a lower speed. All right, here's
your basic engine. So up here in the
cylinder head, you have your intake, an exhaust
valve, and your spark plug. Down here, there's the
crankcase and crankshaft. Here's an exciting-- this
is kind of an inline-four, but you get an idea
of the power strokes. Everybody used to know
this in the old days because they were
excited about cars, so they had a lot of
car-related knowledge, and it's basically
the same idea. But now in the Uber age, we
can't take that for granted. So you've got your
intake stroke top left, and then the cylinder. The piston is pushed back up to
compress the air-fuel mixture. The spark plugs ignite. Notice how there's
two of them here. That gives you some redundancy
as well as more uniformity of combustion, which pushes
the piston back down generating the power. And then finally,
the piston rotates up and pushes the air out. I think this might be
called the Otto cycle. I think a German
guy invented this-- or actually, a French
guy patented it first, but maybe Otto reduced
it to practice first. But anyway, it's a European
invention from the late 1800s, and it really hasn't
changed much-- four-stroke cycle. OK, cooling, as I said it's
a combination of the air and the oil circulation. The FAA wants you to know that
if you're getting the engine is going hot-- again, this is
probably not going to happen to you here at level. But if you're climbing in your
little airplane out of Wyoming on a hot day, you
might end up having to accept a slightly
lower climb rate, boost your airspeed
a little bit, and lower the nose to
get more cooling air. The mixture control, you
don't see this in cars because they have
automatic systems to adjust the air-fuel
mixture and get the right amount of fuel
in there corresponding to the density of the air. But in aviation, you know
there's your little mixture knob where you can
lean out the mixture. The fuel-air mixture,
you start out rich when you're taking
off because you're at a very high power setting,
and the extra rich mixture cools the engine. If you go really
extreme with this, like you just taxi
around for half an hour with the mixture control at
full rich, in some engines you may end up getting lead
fouling on the spark plugs. If you're up cruising and
you lean it out too much then the engine's going
to get a little bit rough, and some of the temperatures
will go too high. On the modern aircraft, you
have very sophisticated engine monitors that tell you all
kinds of information about what the temperatures are. They may help you lean
to the optimum mixture. If you have an autopilot,
it's kind of a good way to invest some of your time
once you're in the cruise. Carburetors, how do they work? If you fly a Piper or a Cessna
you can say that you have a jet-powered aircraft
because there is a jet in the carburetor that's letting
the low-pressure air and this venturi pull little bits of
fuel vapor out into the-- well, I guess that throttle
looks pretty well closed, but ideally the throttle
would be kind of open, and the air-fuel mixture would
be going into the cylinders. Carb icing, so remember,
lower pressure-- as the pressure falls the
temperature will also fall. So even if it's not
below freezing outside it can become below freezing in
the middle of the carburetor, and, therefore, water vapor
that has been in the air can turn into ice and
eventually block the airflow to the engine. So they tell you,
look, well, just detect that by loss of RPM. You know, you're flying along. You should be watching
the RPM gauge. So obviously, you
would notice this and take the correct
action, instead of having a machine that would
figure this out and do it for you. I guess one reason
they don't want to just have carb heat on
all the time is that it robs the engine of some
of its last 10 or 15 horsepower or whatever. So the carb heat because
it makes the air hotter, it's just like going
up to a higher altitude or flying on a hotter day. The air is going to be
thinner, and, therefore, there are fewer molecules
of air to combust, and you won't get as much power. Question. AUDIENCE: What generates
the carb heat of the engine? PHILIP GREENSPUN: What
generates the carb heat? That's a good question. Same thing that
generates the cabin heat. You basically run the air
over the exhaust system before it goes to the
carburetor or before it comes into the cabin. Good question. Yes, so I think 1950s
cars had some kind of automatic
mechanism for this-- it was, you know, buy a metal
valve, and I don't know. The mixture control hasn't
been seen in automobiles for quite a long time. The ignition systems
of aircraft is actually pretty well designed. You have magnetos. You can see them here and here. You can see him
here at the bottom. The left and right magnetos
are geared into the engine, and they generate
their own voltage. So basically, you don't need
to have a working battery or working alternator to have a
running engine unlike in a car. All you need is these. One of the magnetos is still
connected and working properly. So it's totally
separate from what you might think of as the
aircraft's electrical system. And for further
redundancy, each magneto is connected to half
of the spark plugs such that if you lose
a magneto, you still have one working spark
plug in each cylinder. Does that make sense? You can see that in
this drawing here where each cylinder is being
fed either from the green or the blue magneto to one
of the two spark plugs. And you can test to
see if it runs smoothly on either magneto. Your ignition switch
on the airplane will have a right mag only
switch, a left mag only switch, or both mags, which is where
you have normal operation. But when you're
testing on the ground you'll typically see if it
works on either magneto. OK, abnormal combustion,
what can you get? You can get detonation
which is the mixture ignites before the spark ignites. Or pre-ignition, which is the
slow burn before the spark. And detonation I
think is probably the one that's more common. And it could be caused
by improper leaning. Aviation fuel,
basically 100 low led which is dyed blue is
all that you're going to see in the continental US. In the future though-- so low that means it's
lower in less than the stuff that they were making in
the 1930s or whatever. It's still pretty high in led. It's like the super-- it's like the premium
leaded gasoline, I think, of the 1970s. Most engines actually
don't require this. It's just that it takes so
long to get anything done in aviation that they can't put
an alternative certify and get an alternative fuel
to the airports. But, you know, your typical
Cessna or your Robinson R44 with the carburetor,
it doesn't need this lead that's in
the fuel and then gets spewed out
in the atmosphere. It's kind of a tragedy. And it's been made worse
by this ethanol stuff. So the government says you have
to put ethanol in car gasoline. So you can't just go
and take premium car gas from the gas station and
pour it into your aircraft from a technical point of view-- even if it were legal
regulatory-wise-- because the ethanol will
destroy a lot of the fuel system in the aircraft which
wasn't engineered for it. But if you did
have ethanol-free-- there are a few places
that have mogas. They get special
ethanol-free car gas, and lower-performance
aircraft engines will run just fine on them. There have been
committees-- you know 20 years is kind of like
the standard unit of time in aviation. So for about 20
years, people have been working on some kind of
certified unleaded gasoline that will work
with most engines. If you see clear
fuel in the sump, it usually means the airplane's
been left out in the rain, and some water has
gotten in there. And you got to make sure
that you drain that out. So there's drain plugs on the
bottom of the wings typically, and maybe one near the
bottom of the engine that you can see
if any water has gotten into the fuel system. Jet fuel is hazardous
to piston engines. The nozzles are
designed so that they're physically incompatible. You shouldn't be able to put
jet fuel into a piston engine. Occasionally it does happen. I know a guy who
was flying his Piper Malibu all around
the world, and he got some barrels of
fuel delivered to him, and he had to pump it himself. And I don't know,
for whatever reason, there was jet fuel in there. AUDIENCE: So Philip,
you might want to kind of stop [INAUDIBLE]. PHILIP GREENSPUN:
Is the pizza here? AUDIENCE: No, not
yet, but it's noon. PHILIP GREENSPUN: Yeah, well,
whenever the pizza is here. I think we're-- yeah, we'll take
a break as soon as the pizza shows up. All right, fixed-pitch
propellers. So your most basic trainer
has a regular propeller that its angle relative
to the hub never changes. There's also in
higher-performance aircraft, constant-speed propellers where
there's an adjustment mechanism that you can read about-- a mechanical
collection of springs and spinning weights
that will try to keep the propeller
at 1RPM, and that can be a lot more efficient
in different phases of flight. You can see from
this that if you have a constant-speed
propeller, the efficiency across a huge range of
speeds is roughly constant, whereas if you have a
climb prop or a cruise prop it's only working
optimally at certain airspeeds. All right, so if you have
a constant-speed propeller you're now going to
have free power levers. That's the business end of
it and from a pilot's point of view. You'll have throttle
which is the black one on the left, the blue
prop-speed control, and then the red mixture. The FAA, they may
ask you about this. You know they have
this doctrine. It's not really
true of all engines, but the idea is that you don't
want like a high power setting and a really low RPM setting. They claim that that's
making the propeller take such big bites of the air to
keep the low speed that it's somehow stressing the engine. But, again, not every engine
manufacturer agrees with that. All right, let's talk about-- we'll start in on
flight instruments until our pizza arrives. So this is going to be
your reality I would say. Some of the test stuff concerns
the steam gauges of the past that you still see
at flight schools. And that there are some things
that we can learn from this though that we'll get into. There are some advantages. But anyway, let's start
with this six-pack because actually,
the electronic stuff is mostly trying
to replicate what was done during World War II. There's very little in
a modern aircraft that isn't some kind of upgraded
version of what was in a Boeing B29 bomber, so it's worth kind
of knowing where it came from. So you've got your six-pack. You've got your
airspeed indicator. On the top left, you've
got your attitude indicator or artificial horizon. You've got your altimeter
on the top right, vertical speed
coming down around to the lower right, which tells
you how fast you're going up or how fast you're going
down, a directional gyro which is like a stabilized
compass showing you where you're pointed assuming
it's been adjusted properly. It has to be reset to
the compass in flight every now and then. Ah-ha, is our pizza here? AUDIENCE: I wish I had pizza. PHILIP GREENSPUN:
You didn't see any? AUDIENCE: No. PHILIP GREENSPUN: Oh, no. OK, and then you have
a turn coordinator which is another backup
gyro that tells you whether you're turning
left or right and also the coordination. That's just a ball. We'll get into that
in a little bit-- about whether the airplane
is kind of pitched-- improperly yawed. All right, so it says electric. For a gyroscope to keep
spinning that means it's being powered by electric. What else could
it be powered by? Does anybody know? What else is there
besides electricity that can make this thing spin? AUDIENCE: A vacuum. PHILIP GREENSPUN:
Yeah, a vacuum. So in the old days--
you know, again, this is not as common-- you'd have a
vacuum pump on the engine that would generate a force to
keep these gyros spinning. And those were often failing
which had some pretty bad-- AUDIENCE: So these are
the current reality of many of our planes? PHILIP GREENSPUN: I don't know
of how many-- yeah, I guess there's a few Piper Warriors. Yeah, that's a good reason not
to take like the most basic airplane into the clouds. Because the idea is that you're
supposed to sort of notice. Do they have-- I don't know. I guess some of them have
a little warning light when the vacuum pump fails. But in the most
classic situation, you're supposed to notice
as the pilot in the clouds that this artificial
horizon is failing and it's inconsistent
with this instrument. And then you decide which
of the two to believe. Generally, it's this one
because it's more viable. And then you continue
your flight to the cloud without the artificial horizon. Anyway, that's
ridiculous obviously. So, you know the real
IFR airplanes these days have two attitude indicators,
both powered by electric. And you don't have to sort of
notice the subtle sign of them failing. There's just a big flag that
pops up when they fail-- you know, if they lose power
for some reason, for example. All right, the
pitot-static system. So how do you know anything
about your airspeed? There's a tube somewhere on the
airplane usually hanging out under the wing in your typical
trainer or next to the nose. You see them on jets where
the ram air comes in, and the more ram air
pressure there is, then the faster you're going. That can be compared to
the static pressure which comes in from a
static port usually on the side of the airplane. It has to be in some
part of the airplane where the airflow is
suitable for a static port. So the ram air feeds only
the airspeed indicator, and the static source
has to feed the altimeter and the vertical speed. You've got to read this book. There's a couple of
questions about what happens if the pitot
tube gets clogged or if the static port is
blocked and taped over, and that makes the
instruments read inaccurately. So I'd read about
that for the test. OK, airspeed
indicator, here's what I was talking about how in some
ways the old stuff is better. So, look, here's a good example
of how you get more information out of this than
out of the speed tape on the modern instrument. This gives you all of the
aircraft's performance basically. You don't really need
to refer to the manual to see a lot of
important information. Well, don't fly-- you know, the
speed tape might only show you from here to here-- from like 120 knots up
to 150 or something. But here you're seeing,
OK, let's not fly faster than about 208 knots. Unless we have the
flaps out, let's not fly slower than about 58 knots. And even with the
flaps hanging down, we don't want to fly
slower than 55 knots because that's going
to be where it's going to stall at
certain CG configurations and at gross weight. OK, the yellow arc. Well, the yellow
arc is to be avoided unless the air is smooth. So that was actually a
great user interface. And because cool jets
have the speed tape when they make the glass
panels for little airplanes which really don't need that
kind of precision and speed control, they said,
well, let's just have this thing that
the jet pilots have. All right, how does the
airspeed indicator work? There's brass in there, so
it's a cool old-school Sherlock Holmes-style brass instrument. The ram air is coming in. There's a diaphragm that moves
some levers, and eventually the needle swings. Again, you know, you don't have
to design one for your test. You just have to
know that it's going to respond to the ram air. Some of these little
symbols are worth knowing. Probably Va is
the most important because it's on the
test, I believe, as something that
is not indicated on the airspeed indicator. That's the maneuvering speed. That's the speed at which you
can do extreme control inputs and not bend the airplane. Any faster than
maneuvering speed it's possible that you
could yank the yoke back so hard that you'd bend the wings
a little bit or overstress them. The reason it's not indicated
on the airspeed indicator is it varies by weight. And it's actually higher-- that's something
worth reading about-- it's higher if the
airplane is heavier. It's one of the few speeds
where weight is helpful because if it's
really heavy, it's just harder to get the
airplane to perform in some extreme manner. VSO is also worth looking at. That's basically
the speed that's going to determine
how fast you land. That's the speed that
the airplane will stall on landing configuration. So you usually want to
be going at least 20% faster than that to give
yourself a safety margin. OK, here's something from
the New England Air Museum in Bradley, Connecticut--
another great destination about half an hour's flight
away, huge airport, great FBO. They will give you a free car
to use while you're there. It's called Signature
Flight Support there. Anyway, so this aircraft-- I think it's a P40
from World War II, and it can go up to
500 miles an hour. All right, altimeter,
this aircraft is at about 10,000 feet. So notice it has this
little triangular needle at 1 that's telling
you that it's at 10,000 feet. And then the longer needle
is reading in hundreds, so we're at about 10,200. And sure enough, we can
see this is indicating you know 10,180, so 3 needles. Usually, the ones you're
going to deal with are this one at the top
here for thousands of feet and this one for
hundreds of feet. OK, so back in the
old days before we decided to dig up all the coal
and the oil and set it on fire, this was our
standard atmosphere, and it was wonderful. And it was always 15
degrees at sea level. And it was always 29 or
niner two for pressure, but now we've ruined it. The standard
atmosphere is the basis for a huge number
of calculations. The altimeter, we're going
to look at this again. It has these android
wafers that, I guess, provide a reference pressure. And somehow the difference
between what's in there and what's coming in will
make the needles move. That's about as
much as I know not being a mechanical engineer. An important factor though
with all these altimeters is you can set it to correct
it for whatever the prevailing pressure is locally. So that's what you really
need to know as a pilot-- that if they tell you
the altimeter setting is 3053, that you turn it until
you see 3053 in the window. It's worth knowing these
altitude definitions. The most important for
determining aircraft performance is going
to be density altitude. That kind of tracks
the actual number of molecules that are in
a given volume of air. If you're flying
along, you'll be looking at indicated altitude. That's kind of how aircraft
tend to be separated. Everything else is
kind of nice to know. Pressure altitude, we
talk about it a lot, but I don't think
it's really often used in practice for much. Actually above it--
I shouldn't say that because above
18,000 feet it's used. You always set the
altimeter to flight level-- you know, 220 instead
of 22,000 feet. If the temperature standard
pressure altitude and density altitude are going
to be the same-- so that would be, again, 15
degrees at sea level and cooler as you go up-- the pressure altitude will
also equal the true altitude. So that's the actual
height above sea level, again, in standard
atmospheric conditions. We'll talk about this at
a few times in this class. But when it's hot the entire
Earth's atmosphere expands, and if we were to cool the
earth down near absolute zero, the atmosphere would contract. We might read on our altimeter
that we were at 18,000 feet when we were only,
you know, an inch above the ground because the
Earth's atmosphere had shrunk to only two inches in size. All right, when you're flying
indicated altitude there's an expression called "high
to low, look out below." Because if you go
from an area where there's a high-pressure setting
to an area where there's a low-pressure setting,
you'll inadvertently descend by 1,000
feet if you just follow what the altimeter is
telling you without resetting the altimeter. Same issue when you go from high
temperature to low temperature. So I just came back from
Jacksonville, Florida, in the Cirrus, so I went
from high temperature. And at an indicated
altitude of 3,500 feet, I was actually a bit higher
above the earth than here in cold New England. So that's another
thing to be aware of, and this becomes
important for instrument flying in very cold conditions
like up in the Canadian Arctic. If you fly indicated altitudes
when it's extremely cold, you'll be closer to the ground
than they budgeted for when they designed the procedure. OK, vertical speed, if
you want to maintain 500 feet per minute
climb rate or descent rate for your
passenger's comfort, then this instrument
is your friend. It does lag so you can't
really use this to-- all these instruments
are outputs, not inputs. Your inputs as a pilot are
the attitude and the power. So you set a power. You set an attitude like
a little bit three degrees nose up, and then you
use these instruments to verify that you're getting
the performance that you want. Especially true for the
vertical-speed indicator because the instrument
itself has lag in addition to the lags that come from just
the inertia of the aircraft. OK, under the hood it's
gotten this calibrated leak. I don't really-- anyway,
it's another fancy instrument than a mechanical engineer
should tell you about. All right, gyroscopes,
the main property is you can use them for
an aircraft instrument because it will try to stay
where it is relative to space. It has to be corrected. In the instruments, it's really
where gyroscopic precession has to be considered
because think about it, you're going to be showing
the pilot various things on the face of the instruments. So you want to sure
that the deflections correspond to what's happening
out there in the real world. Again, this is covered
in the Pilot's Handbook. This just tells you, again, if
you kick a gyro up at the top, instead of the axis of the
gyroscope rotating downward, it's actually going
to yaw to the left. That's gyroscopic precession. Turn coordinator, it
has a gyro to tell you that little airplane, if you're
doing a standard rate turn, it'll go to this point here. That's a two-minute
turn that'll take you two minutes to go 360 degrees. And it's a backup to a
vacuum-powered attitude indicator. It also has this completely
separate function of a little ball in-- I think, it's in
kerosene actually-- so it's a little ball in fluid. And in a perfectly
coordinated turn, you should actually
feel like you're just standing on the ground
at 1G, and the ball should stay right
there in the center. All right, turn
coordinator, it can tell you whether you're slipping,
skidding, or coordinated. So if you're
coordinated, as I said, it's just like sitting in
a chair and not moving. If you're slipping, if you have
any trouble visualizing this you can just reflect
on the fact that you have to step on the
ball to fix the problem. So here your airplane's
in a right turn, and it's telling you you have
to step on the right rudder and bring the nose more
around to the right in order to be coordinated. So that is a slipping turn. So here's our airplane. We've banked the
wings, but we've got the nose still
kind of pointed where we used to be going. So it's telling us
you need to kick a little bit of right rudder
and have a coordinated turn. Skidding is the other way. For some reason, we have too
much right rudder in there, and we need to back off of
it or hit some left rudder and bring it back. Again, this is
something, it'll become-- you know, eventually you
develop a sort of a feel for it in the seat of your pants, and
you'll just do it naturally. And actually, modern
aircraft don't have a whole lot of,
what's called, adverse yaw, so if you try to
turn them, they're not really going to
get out of coordination to any large extent. All right, attitude indicator. If you're either in level
flight or on the ramp, this little airplane
pointer here in the middle-- that little orange thing-- is just something that you
can rotate up and down. It's basically just
a reminder for you of what attitude will
produce level flight. It might be a couple
degrees pitched up or down, but you just set it
to whatever it is. This is a gyro that's free
to move in two directions, and as it moves, it
moves this bank index, I guess, on the face of the gyro
is what they're calling it-- or maybe that just
is the bank index. It's moving the whole
artificial horizon on the face of the gyro. So the important thing is
it's a gyro at 2 gimbals. In aerobatic airplanes, this
design doesn't work very well. It tends to get damaged by
all of the extreme maneuvers and g-forces. As a pilot, what do you
need to know about this? It's worth knowing
how to read it. In your flight training, you'll
do, so-called, steep turns where you'll bank to
a 45-degree angle. It's mostly a visual maneuver
where you look outside, but the attitude indicator
is a good reference, again, to see whether the picture that
you've got of a natural horizon actually does correspond
to a 45-degree bank. If you go up, I think if you
go beyond 60-degree banks, it's time for your aerobatic
airplane and your parachute. That pointer at
the top generally will be pointed up at the sky
however you're maneuvering. We'll see this in a moment here. So you can see, let's just
pick a level right turn. So over here, you say,
well, that thing at the top isn't really pointed
up at the sky. It's just pointed off to
the left but think about it. They're just showing
you the instrument as you would see
it in the cockpit. So because the airplanes
turn to the right, that top pointer would
actually correspond to straight up into the sky. But as you see, it's kind of
the same picture you would get. You're more or less not
pitched but you are banked. If you're going up
climbing right bank, you see you're just pitched
up a couple degrees. There's a little bit more
blue here versus here. As an instrument
pilot, you'll get very good at seeing small
differences-- just one or two degrees of bank or pitch here. We're about to go into
the magnetic compass, so let's take a
break here and we'll wrap this up after
everybody has their pizza. A few things to remember
about magnetic compasses, and then we're off to Oshkosh
which is going to be more fun. The most important thing
is that it only works when you're straight and level. And the fundamental
insight for this is the compass is
a horizontal thing. It's only designed
to move horizontally. So if you start tilting
it, tilting your aircraft, one big part of it-- big part of the
problem is the compass tries to still point itself
towards the magnetic north pole which will cause it
to rotate a little bit. It's a little bit
hard to explain without thinking about
it and reading about it in the Pilot's Handbook. But the takeaway is that
because it has inertia, and because it's
not really fully free to rotate to point
in three dimensions down to the north pole, you get
all these bizarre errors. Like if you turn away
from a heading of north, it'll initially show a turn
in the opposite direction. And if you accelerate because
of the inertia, it'll-- let's see, accelerate
north, and yes. All right, we'll get
into that in a moment. Even I can't remember it. Just remember don't
look at it unless you're straight and level. The true magnetic-- I think
actually the north pole-- the magnetic north
pole, I heard recently there was some kind of
significant movement. Anyway, it's moved
quite a bit since 1632 as you see here on this chart. Because true north is not equal
to magnetic north, and the kind of primary source of direction
that you have in your aircraft is a magnetic source,
on the charts, you end up getting these
isogonic lines that tell you how much correction to apply. So here you can see
14 degrees west. That tells you-- because if east
is least, and west is best-- if we want to fly
straight true north, we actually have to
steer zero plus 14. So zero is the true
north course, add 14. And if we see 14 on our
compass, or between 10 and 20 on our compass, between 1 and 2
I guess it would be indicated, then we're heading true north. If you forget all of this
stuff that I'm telling you-- which I hope you will because
this is a very tedious area-- you can cheat. So look at this VOR. The VOR tells you this
is the Block Island VOR. This is another
great place to fly. So you land there. You walk to the beach. You skip out on the ferry ride. This is the best arguments
for general aviation aircraft are almost always
places that are islands, and you can't drive there
on your Honda Accord even if you wanted to. So but you see here, the zero
magnetic line is not aligned. The charge is in true north. So there is your true north. There is your zero magnetic. So you can just see
that the variation here is about 14 degrees. You wouldn't even
need-- and you can also that east is least,
west is best rule, you can rederive it just
by looking at any VOR. Except don't look
at a VOR in Florida because that's where
there is no variation. But almost any other VOR
you can look at and see what the new rule is. All right, magnetic deviation. If you have stuff
in the airplane, it will cause the compass to
be a little bit inaccurate. So they give you this
compass card here underneath, which will give you usually
one or two-degree changes at the most for how you would-- you know, if you want to
fly north magnetic heading, you might actually steer,
I don't know, zero-point-- steer a course of
one or two degrees. You know, if you bring stuff
into the aircraft that's heavy and metal or magnetic,
that can affect your compass. And actually, in an aircraft
with heated windshields, if you turn on the heated
windshield for anti-icing, and in jets, it's
kind of standard to fly with them
on all the time, the compass becomes useless. The heated windshields
throw it off by 90 degrees. All right, in the
lowest end airplane, they'll have a directional gyro. Because of all of those
compass errors, you as a pilot, will basically, just
every five or 10 minutes if it's a really old and bad
DG, or maybe every half hour if it's a decent new one, you'll
just look up at the compass when you're in level
unaccelerated flight, and you'll reset with this
knob here down at the bottom. You'll twist that to
align the directional gyro to the compass. So the compass is the authority,
but it's only an authority when you're straight and level. OK, under the hood, notice
that this, unlike the attitude indicator, this
only has one gimbal. And that's really the takeaway
for why the attitude indicators tend to break more often
than these other instruments because they have two
gimbals and they're just a little more fragile overall. Horizontal situation,
everything in flying, they've tried to make
it more idiot-proof, and the HSI is a great
example of something that was figured out,
I don't know, maybe in the 50s or maybe earlier. They said, what if we just
take that DG and we put an indicator on here. This is showing we're trying to
go on a heading of about 010-- just slightly north. That's this yellow pointer. We are actually going on
a heading of about 020. Maybe that's because
of a wind correction. There's a wind coming
from the right. And it also
integrates your line. See it shows you with this
course deviation indicator that you're slightly to
the right of the course. The course is a little
bit to your left. And actually, this
person, I think, this pilot is flying an
Instrument-Landing-System approach. This yellow trapezoid
there on the left and right is showing
you where you are relative to the glideslope. So you're right
on the glideslope. So basically, all
the information that you need for your flight
other than the attitude is on this single instrument. If you have everything
set up correctly the radios or the
GPS, you really don't need to look
anywhere but here and at the attitude indicator. It's a pretty nice idea. And this is replicated in
all of the glass cockpits. All right, technically
advanced aircraft, here's a photograph of the
latest and greatest Cirrus SR22 or 20 cockpit. You have two big screens. One's usually called the PFD-- primary flight display--
one's the MFD-- the multifunction
display-- that shows you maps and weather and traffic. This idea came from the big jets
from the 80s, I guess, and 90s. It was adopted in
the Cirrus in 2003, pioneered with an
MIT spin called Avidyne which is
a local company. Garmin kind of took things over. And most of the aircraft
today come with Garmin. G1000 is a brand name
that you might have heard for a Garmin product. It's pretty popular. In some ways, people
with older aircraft are almost better off right now. There's this huge
stream of retrofit stuff that's very innovative, more
so than the comprehensive glass panels. And usually, for $30,000
or so an older plane can be brought up to
the modern standard. OK, what if things are
not going well at all? The ultralights tend to
come apart in flight. Certified airplanes
virtually never come apart. They're just so over-engineered
that wings don't fall off, struts don't fail. But the two brothers-- the Klapmeier brothers,
from Wisconsin, I believe-- although the company
they started, Cirrus, is in
Duluth, Minnesota-- they say, look, this
parachute would give people a lot of comfort, and
there are some situations in which it could be useful
even in a certified airplane. So they added it in the Cirrus. And you pull it, and the rocket
chutes the parachute out, and you float down. It's becoming more
and more popular. I thought it was a
payload-hogging waste of money when I bought the
Cirrus in 2005. And now that the engine
has 2,000 hours on it, and I'm flying at night, I
think that's pretty good. That's a pretty good parachute. I don't even mind
the $15,000 that we paid to have it all repacked
at the 10-year point. All right, summary,
so piston engines, they're very fuel-efficient
compared to jets at these power settings. They have quirks
which sounds bad. You know, one cylinder
might be running rough, but it's better than
in a jet world where if things aren't perfect, the
engine just quits or explodes or something. So turbine engines seldom go
bad, but when they do go bad it's often with no warning. Here's your six-pack. The altimeter,
remember, is essentially measuring a percentage
of the atmosphere that you're above or below. Compass is full of errors except
when you're straight and level. And also the aircraft
manufacturers are really systems integrators. They're buying the
engine from somebody. They're buying these
instruments like the Garmin G100 from somebody. Study pitot-static failures
and the compass areas. And they're on the exam,
and they're not intuitive. Questions. This is another picture from
that air museum in Bradley. They have one of the handful-- it's not flying, I
don't think, but it's restored-- a Boeing B29 bomber. And if you want to know
why I get defriended all the time on Facebook,
I posted this picture of their turret computer, and I
said I found the original iPad in the museum. That was hashtag not funny. [LAUGHTER] All right, any questions or
should we go into Oshkosh? We can have questions. Don't ask about those
brass and neural things because I was a math undergrad
and EECS grad student.
