Airplane Flying Handbook (AFH)

by US Department of Transportation, Federal Aviation Administration
2021, 406 pages
reviewed by T. Nelson

ut your phone on ‘vibrate’ and your vibrator on ‘phone’ while you read these two interesting books on airplanes.

The first one is an authoritative description of what airplane pilots have to do to avoid an “unintended outcome” as the authors delicately put it. To liven up the text, they alternate between this and other imaginative euphemisms like “unfortunate consequences”, “unwelcomed consequences”, and my favorite: “level flight will not be possible.” They all, of course, mean the same thing: ATC is not going to bother telling you to have a good day.

The book is divided into sections for single reciprocating engine airplanes, two-engine props, turboprops, jets, and light sport aircraft (LSA). There's nothing about helicopters.

To hear the FAA tell it, those two-engine props are the worst. They're virtual death traps. Spin, which is what happens when the airplane stalls and rotates vertically on its way to an 'unintended consequence' is unrecoverable in a twin engine and should never be practiced even during training. Other mistakes that can cause bad hair days include forgetting to use your checklist after a go-around (a go-around not, they emphasize, being a sign of bad piloting), having an engine fail during take-off, having a fire, electrical failure, running out of fuel, having a dead battery, running out of coffee, or any of dozens of other bad things that can happen during a flight.

This book will also tell you why beginning pilots fly around in circles, then squircles, and then work up to amusing anatomical shapes.

Turboprops are quite technically interesting. They're gas turbines that drive a propeller but they also get 10% of their power from the exhaust. Unlike regular engines, they can produce reverse thrust. To do this, the propeller blade angle is rotated to push air forward instead of backward, while the engine continues rotating in its normal direction. This differs from turbojets and turbofan jet engines, in which thrust is diverted by positioning a target in front of the exhaust (or, in some designs, in front of the fan).

Rotating a propeller to make the blade parallel to the direction of travel is called feathering. It's essential when an engine goes out because a windmilling propeller causes an enormous drag that makes the airplane hard to control. Needless to say, that's especially bad in a twin engine prop.

It's clear from this book that flying an airplane is much harder than driving a car, which is probably why we don't have flying cars. For one thing, an airplane engine is always run at the redline and is easily damaged. There are foot pedals (left and right rudder and left and right brake) and of course a variety of gauges, levers, switches, LCD screens, and indicators. This book gives lots of excellent advice about what to do in a variety of perilous situations, along with technical details about trim, bouncing, ground effect, crabbing, drift slip, yaw, drag, stalling, glide paths, and shock waves at speeds approaching Mach one.

They repeatedly emphasize that the pilots should not touch anything after landing until the plane has reached the terminal and come to a complete stop (which as we all know they also say to the passengers). The reason is not just to put their tray tables up, but because many pilots get the flap lever confused with the landing gear retraction lever. Even though there's supposed to be a switch to prevent gear retraction on the ground, evidently pulling that lever is a common and probably very embarrassing mistake. Perhaps anticipating the recent Boeing fiascos, they also advise the pilot to ignore when a door pops open during flight and focus on flying. My favorite, though, is where they advise you in the last chapter not to attempt to crash between two trees while airborne. I think this is really good advice, and it's wonderful to have a government that cares enough to tell us things like this.

apr 05, 2024

Pilot's Handbook of Aeronautical Knowledge (PHAK)

by US Department of Transportation, Federal Aviation Administration
2023, 522 pages
reviewed by T. Nelson

his one reads like one of those mandatory training courses the US Government forces people to take, knowing they have a captive audience. For example, the main character trait of an accident-prone person, they say, is a disdain for rules. You should always follow the rules, and your beloved leaders are here to help you with that.

They also have many useless mnemonics for you to learn: The PAVE checklist (Pilot in command, Aircraft, enVironment, and External Pressures); the Five P's (the Plan, the Plane, the Pilot, the Passengers, and the Programming); the DECIDE model (Detect, Estimate, Choose, Do, and Evaluate); the CARE checklist, the TEAM checklist, the SAFETY checklist, and a bunch more.

Of course, these books are free to download, and flying is a serious thing, so we can't make fun of them too much. And they're much more interesting than the stuff the IRS publishes.

To drive the points home, they give us thrilling anecdotes, like this one (shortened here):

A pilot calculated that he would have only 10 minutes of fuel remaining, but he was determined to keep on schedule. After landing, the pilot realized that this could have easily resulted in an emergency landing.

The next section tells us the parts of an airplane, making no assumptions about the pilot's background knowledge:

The propeller, mounted on the front of the engine, translates the rotating force of the engine into thrust, a forward acting force that helps move the airplane through the air.

Still, I would guess that beginning pilots would probably know this already.

While this is nobody's idea of an exciting book, I must admit that the illustrations are excellent. For instance, there's a nice diagram on page 168 showing how a carburetor works. Then on page 169, there's one showing what happens when it's coated with ice. There's also a beautiful map showing the isogonic lines of magnetic field declination on page 226, and an interesting brief history of aviation. But lest the narrative get too exciting, on page 371 they go back to their real interest: inspection regulations and instrumentation.

For instance, the book says airplanes are still using barometric pressure to determine their altitude. This is called pressure altitude and it's why airports tell approaching planes corrections to the barometric pressure at their location: normal weather differences would result in errors of over 1800 feet. 'Radio' or radar altimeters, while more accurate, only tell you the altitude above the ground directly under the plane, which could differ from the altitude of the airport.

There are interesting sections on vortices, ADS-B and other navigation aids, and the meanings of all the signage, lights, and markings on runways. The manual repeatedly warns not to cross a holding position marking without ATC permission. Doing that can get an FAA Pilot Deviation filed against you, which starts with that dreaded message from ATC to get a pen and paper handy.

For those of us whose only knowledge of airplanes is that our seat cushion can be used as a flotation device, this book may be mildly interesting. But for pilots, the fact that it comes from the horse's mouth means it's essential.

apr 07, 2024

Fundamentals of Aerodynamics, 5e

by John D. Anderson, Jr.
2011, 1106 pages
reviewed by T. Nelson

hy is it that even when we put our phones on ‘airplane’ mode, they exhibit such poor flight characteristics? They just fall straight down and smash on the floor. Why does a spinning golf ball fly almost straight up when it's hit? And how did airfoil shapes affect the armistice after World War I?

The answer, of course, is aerodynamics. Cell phones are like the proverbial barn door, which has a lot of drag but little lift. The dimples on a golf ball shorten the transition from laminar flow to turbulent flow, which reduces pressure drag (D_p). And after the famous aerodynamicist Ludwig Prandtl showed that a thick airfoil produced more lift than a thin one, their incorporation into Anthony Fokker's Dr-1 “Red Baron” triplane was so effective that the Allies demanded that they be handed over after the war.

After 200 pages reviewing the math (mostly calculus and linear algebra), the rest of this book, written for aeronautical and aerospace engineers, is in three parts: incompressible flow, compressible flow, and viscous flow. The relation, pounded into every pilot's head, between angle of attack α and stall speed is explained in detail.

They're not just for engineers: suppose you jumped out of a tall building with only a conference table strapped to your back. Clearly you would want to reduce your acceleration. To do that, you'd need to maximize your lift by adjusting your angle of attack. But not too much, or you would raise your coefficient of drag and cause a stall. (Of course, you'd have a better chance if you also brought a rudder and ailerons with you.)

The reader might be surprised to learn that a rotating cylinder produces much more lift than a well designed wing. This is called the Magnus effect, and it's used on spinning missiles. The Kutta-Joukowski theorem L′ = ρ_∞V_∞Γ, which relates the lift to the air density, airspeed, and vorticity, tells us that circulation around the body produces lift.

Friction is also necessary for lift. Of course it produces drag as well, and vortices behind and below an ascending airplane have caused many crashes. Drag can be produced by flow separation, where the slipstream detaches from the wing, producing turbulence. At speeds above Mach 1, drag increases dramatically and shock waves waste even more of the engine's power.

At speeds up to Mach 0.3, the forces are easily described by algebraic formulas. At supersonic speeds, second-order partial differential equations are needed, many of which can only be solved by computational fluid dynamics software. Wave drag becomes significant, which means that swept wings and thin airfoils are essential to reduce drag to tolerable levels. It's essential to model shock waves. Heating from shock wave interactions was missed during development of the X-15 and burned a hole in the fuselage. Airfoils were so pointy that the razor-sharp leading edge of the Lockheed F-104 wing needed a protective cover to prevent injury.

Aerodynamic heating increases with the cube of velocity, so at hypersonic speeds heating becomes a critical factor. At 2000 K, oxygen starts to dissociate, which means that all the formulas that assume γ=1.4 for air no longer work. At 4000 K, nitrogen also dissociates, and above 9000 K both nitrogen and oxygen become ionized. Heating at a stagnation point, such as at the nose, varies inversely with the square root of nose radius. This is why ICBMs (which come in at Mach 25) and the Space Shuttle all have blunt noses despite the increased drag. Even so, the Space Shuttle experienced 45 watts per square centimeter at the nose but less than 10 further back. So, if you're jumping out of a space shuttle 100 miles up, a thin barn door, even one made of tungsten or reinforced carbon-carbon, might not save you.

Anderson tries to make the subject interesting, but often at the expense of excess words, which engineering students dislike. The book desperately needs a table of symbols: μ means either Mach angle or viscosity coefficient. T means temperature or thrust, λ means bulk viscosity coefficient or strength of source, and γ means either difference in velocity across a section of the wing, specific weight, or heat capacity ratio of a gas (c_p/c_v).

Inadequate index. Uses inconsistent units, which makes it harder to use as a reference.

may 04 2024