please direct your attention to the flight attendants

You know the safety briefing that flight attendants give to you when you fly on an airliner? Well private pilots are required to give a version of it to their passengers too. I ran across a checklist for a Piper Arrow that listed an extremely detailed briefing, which got me thinking as to what parts of it are required.

FAA regulation 91.519 covers this topic. Basically, you must make sure your passengers know:
- when and where they can smoke
- how to use the seat belts and when to have them on
- location and operation of normal and emergency exits
- location of survival equipment
- information on ditching (landing in water) if appropriate
- use of (normal and emergency) oxygen equipment

Regulation 91.21 also covers the use of portable electronic devices. The current version, as of 2009 states:

(a) Except as provided in paragraph (b) of this section, no person may operate, nor may any operator or pilot in command of an aircraft allow the operation of, any portable electronic device on any of the following U.S.-registered civil aircraft:

(1) Aircraft operated by a holder of an air carrier operating certificate or an operating certificate; or

(2) Any other aircraft while it is operated under IFR.

(b) Paragraph (a) of this section does not apply to—

(1) Portable voice recorders;

(2) Hearing aids;

(3) Heart pacemakers;

(4) Electric shavers; or

(5) Any other portable electronic device that the operator of the aircraft has determined will not cause interference with the navigation or communication system of the aircraft on which it is to be used.

(c) In the case of an aircraft operated by a holder of an air carrier operating certificate or an operating certificate, the determination required by paragraph (b)(5) of this section shall be made by that operator of the aircraft on which the particular device is to be used. In the case of other aircraft, the determination may be made by the pilot in command or other operator of the aircraft.

I assume "an operating certificate" is something that applies to airlines. So...if I read this right, then when operating a general aviation aircraft under VFR flight rules, I can allow people to use Cell phones in flight? And even if I'm going to operate IFR, I can still have them used if I determine that it's safe?

I'm stunned. For some reason, I assumed there was a hard "don't use Cell phones in an airplane or you'll surely die!" regulation somewhere. Since airlines prohibit their use, I had always assumed that the same rule applied to me as a generation aviation pilot. My briefing (to flight instructors) has pretty much been "seat belts fastened? Cell phones off?".

Guess we learn something new every day.

hollowpoint

There was a fascinating article in the New Yorker about John Coster-Mullen, a photographer who over many years and using secondary evidence, puzzled out the designs of the first atomic bombs dropped by the United States in 1945. The article is a long but fascinating read, about his process of piecing together clues and photographs and fragments saved by machinists and other people who worked on small pieces of the bombs.

Coster-Mullen has also produced a book about his findings, published in 2003: Atom Bombs: The Top Secret Inside Story of Little Boy and Fat Man. His partial diagram of the internals of the Little Boy (the Uranium-fission bomb; the Fat Man was based on Plutonium) is available on Wikipedia under a creative commons license.

I remember when these diagrams first surfaced a few years ago, presumably when this the book first became available. One very interesting item about this process is Coster-Mullen's re-discovery of the central Mechanism of Little Boy. The bomb worked by slamming two sub-critical pieces of Uranium-235 (which undergoes self-accelerating fission) together to form a super-critical piece. The assumed setup always has been that a slug of Uranium was fired into a cup Uranium. The fact was the opposite, as illustrated in the diagram. The target was a cylinder held in the bottom of the bomb, and a hollow cylindrical projectile was fired at it, embracing the target slug.

My interest in this subject is about the physics involved, rather than the destructive possibility. It's also about the process of secrecy vs. discovery, and figuring out how something was made, even as monsterous a device as that one.

carb heat: the neglected control

So far, in my very brief flying career, I haven't thought much about carburetor ice or carburetor heat, other than as it pertains to decent and landing procedures (any time you reduce throttle in a C-150, or any time the engine is running below 2000 rpm, turn carb heat on).

And there was the various written materials and the tests, which contain questions like "what is the sign of carburetor ice in an airplane with a fixed-pitch prop", the correct answer to which is "a drop in engine rpm".

Those things provide one side of the equation; how to find carburetor ice if you know you're looking for it. After my flying experience yesterday, I think the other half of the equation should be added to flight training with a little more emphasis. That is, what should you do as a pilot to make sure that carburetor ice doesn't sneak up on you? The reason for this post is that I almost had an engine fail yesterday, and I'm pretty sure it was because I had bad carburetor icing and I didn't realize it until almost too late.

My new rule in flying: If the engine does something unexpected, particularly if it runs rough or the rpm drops unexpectedly, turn the carburetor heat on and leave it on for at least a minute or two.
Codicils to this rule are as follows:
- This is especially true when flying and airplane with a carburetor (not fuel injection).
- This is especially true when flying and airplane powered by a Continental engine.
- carb heat enrichens the mixture going into the engine. Therefore the one exception to this if you've flown from low to high altitude and forgot to lean the engine, it will already be running too rich, in which case carb heat will make the problem worse.

It takes several seconds for carb heat to take full effect. You can tell if you had carb ice because when the heat is applied, after a few seconds, the rpm drops a LOT but then climbs back up (after the ice is all melted).

Along with the last point: part of the run-up procedure for any piston-powered airplane is to test the carb heat by turning it on and making sure that the carb heat control works. I did that yesterday, and I definitely got a respose. However, thinking back, I think the rpm may have decreased more than usual--in retrospect, the airplane may have already been developing carb ice on the ground.

So as with most things, it's mostly a matter of being aware. For pilots, one thing to be very very aware of; the engine doing funny things can be a sign of carb ice, to which there is one and only one reasponse: pull the carb heat control and leave it there long enough to clear any ice.

And since I like pictures, here's my friend from yesterday:

leaving the cradle for the first time

Forty years ago this week, the crew of Apollo 8 were the first humans to go into orbit around another body besides the earth. The three astronauts, Jim Lovell, Frank Borman and William Anders remembered the mission this week.

The mission was a very big step in the Apollo program. It was the first use of the Saturn 5 rocket for a manned launch. The Saturn was necessary to provide the trans-lunar injection maneuver to fling the spacecraft from earth orbit to lunar orbit. Along with those physical capabilities, there were several orbital navigation tasks that all had to be performed correctly to get the spacecraft to the moon and back.

Apollo 8 also had a large cultural significance. The crew made a television broadcast from lunar orbit and read from the first chapter of Genesis, the bit that begins "In the beginning...". They also took a very famous series of photographs taken, some of which were the "earthrise" photos:


By the way, the Apollo 8 Command module is in the Museum of Science and Industry in Chicago, Illinois.

breathe in, breathe out

In September, I wrote a very long text-heavy post about the process of internal combustion engines and what things can be adjusted.

I'm getting back to that, so I've attempted to produce a diagram that partially illustrates the process here:


Each thing in parentheses can be adjusted; some things only as part of the design of the engine, others are adjusted when the engine is running. If any of the items fails to work, the engine will not run.

Adjusting the performance of an engine (of given displacement) involves changing one or more of the items in the diagram. The engineering challenge is that such a change also requires you to change other aspects of the engine to compensate.

For instance, the ignition timing and mixture are intimately involved with each other; they need to change in relation to each other for the engine to keep running. If you stomp on the gas and the engine hesitates, it means that when the throttle opens quickly (increase in the effective volumetric efficiency), the mixture and ignition timing aren't changing properly to compensate.

I put in the mechanical removal of heat because that's a critical (and limiting) parameter of the Volkswagen air-cooled engine (like in my beetle). It's essentially a function of the fin area of the cylinder heads and the airflow around the engine. There are lots of ways to increase the power being developed by a VW engine. You can, for instance, make the intake and exhaust system much less restrictive to make the engine breathe better. However, that only increases the load on the cooling system and so makes it easier to overload and overheat the engine.

My next task with my engine is to decrease the compression ratio of the cylinders down to what it should be. I think it's been increased by accident, by people adding used heads without adjusting things properly. That will decrease the burden on the engine's cooling system and allow me to adjust the ignition and carburetion systems correctly, and hopefully stop the exhaust valve from stretching.

football season

Our third cat (Thrice) arrived Thanksgiving day a year ago. Thrice and Pangur are only now relatively Ok with being around each other, sometimes. However, we had a real breakthrough the other day watching football. Here's Jasper, Pangur, and Thrice all together with us watching football the other night.

Jasper in the orange cat at the bottom. Of the grey cats, Pangur is to the right and Thrice is to the left.