Then having a pressurization system didn’t do him any good?
Well, he didn’t need it anyway. Pressurization is only required when you’re at high altitude-ten or fifteen thousand feet or more. Circling over New York, he wasn’t much higher than your tallest buildings. I doubt he ever took the plane up above two thousand feet. Probably less than that. He had no need to pressurize the cabin, or use oxygen, or turn on the heat. It’s only at higher altitudes, where the air becomes very thin and cold, that you need those devices.
I see. But Mr. Harris mentioned to you that he noticed these elements when he first photographed the plane in flight?
Harris is quite observant, I’ve found. He’s also something of an airplane buff, so you might expect him to notice things that another person might miss.
Can you continue?
Certainly. The point is, I think, you’ve got to realize that the plane had already been converted to passenger use when he decided to turn it back into a bomber. He’d already got the pressure system and the heat and all that stuff built in. Now he didn’t need any of those items for his bombing scheme, but it would have made for a lot of extra effort to remove those items from the plane, and he had no reason to remove them. They weren’t in the way. It’s the same as the air conditioner in your car. You don’t use it in the winter, but that doesn’t mean you remove it.
I understand that.
Now, as for the bomb bay, that part of the plane had been welded shut and completely rebuilt inside the fuselage for passenger service. Also, the machine-gun blisters had been removed and those cavities in the skin of the plane had been covered over with riveted plates. And he’d installed rows of double-pane observation windows along either side of the fuselage, so that the passengers could look out from their seats. Some of that he left alone when he did the reconversion. But obviously he removed the seats and the flooring and installed a complete bomb-rack system and a new set of bomb-bay doors in the belly of the plane.
There was a point early in the case-perhaps in the very early afternoon while Craycroft was circling overhead-when Mr. Harris expressed an interest in the communications systems and particularly the navigational systems.
Yes, I talked to him about that. He seems to have done some fascinating detective work at that time.
What was your impression of Harris’ analysis of the equipment?
I don’t think he was making a risky assumption about it. Some people have accused him of that, haven’t they?
It’s been suggested he was hasty.
He wasn’t. He knows these airplanes fairly well, don’t forget that. And he’s a reporter-trained to observe and interpret.
He concluded that the primary system was radio-oriented. And that jibes with your knowledge?
Absolutely. Both B-24s we received from Aero-flight were equipped with radio-beam navigation compasses.
There were also magnetic compasses aboard?
Yes. Carefully corrected for the metal in the airplane.
Were those the original equipment?
Not on our two B-24s. I would assume he installed a new magnetic compass on the B-17 as well, but we don’t know that for a fact, do we?
The evidence we have suggests it.
He had installed a LORAN system as well in one of the two B-24s. That’s similar in design to a radiocompass, but the two systems have different functions.
Did he have both systems on his B-17?
No one seems to know that. It’s quite certain he had a standard radiocompass.
Can you describe the difference, in layman’s terms?
Certainly. A radiocompass picks up a signal from a broadcasting tower on the ground. The location of that tower is known and programmed into your radiocompass. The simple computing device in the compass gives you a readout of your course. The direction you’re traveling, relative to the ground beacon. A LORAN system, on the other hand, picks up signals from two or more separate broadcasting stations on the ground. Again these are of known location; each broadcasts on a different wavelength or with a different code signal. The LORAN receiver absorbs these signals and computes on the basis of geometric triangulation, also taking into account the relative strengths of the signals it receives. As a result it gives you a readout of your location at any given moment. The acronym stands, loosely, for “Long Range Radio Navigation.” But the difference between the two systems is basically very simple. A radiocompass tells you the direction of your heading. A LORAN receiver tells you your exact location. Have I clarified it for you?
Perfectly, thank you. Now, the question became rather crucial and heated, didn’t it, whether Craycroft also had a gyrocompass among his instruments?
I wasn’t there at the time, of course, but I’m told that became a heated issue, yes.
Can you comment on it, in retrospect?
I would have to agree with Harris’ judgment again. The chances were he didn’t have a gyrocompass.
Why not?
The gyrocompass is one of those gadgets you have if you’re very rich or very poor. In airplane terms, I mean. Craycroft was middle-class. He wouldn’t have had one. Let me put it this way. If you have a small private plane, chances are you’ll have only one compass. It’ll be a gyro, most likely, because they’re more dependable for short-term use than magnetic compasses, whch can be deflected by heavy metal deposits nearby. On the other hand, if you’re a huge airline and you operate huge modern jet airplanes, you’re going to want to have every kind of navigational system that’s available. You’ll have probably ten different systems aboard, and one of them will be a gyrocompass-just part of the package, one of those planned redundancies so that you can double-check one instrument against another and get confirmation of your readings. But if you’re in the middle class-rich enough to afford a few extra safety gadgets, but not profligate enough to carry tons of extra instruments-then you’ll probably dispense with the gyrocompass. You’ll have a magnetic, and you’ll have one or two types of radiocompass, and that’ll be that.
You seem quite certain of that.
I am. I’m airplane people, remember? So is Mr. Harris. Also, there’s the fact that I’ve got two of Craycroft’s planes in my custody, so to speak, and neither of them has a gyrocompass-even though both planes were originally equipped with them. They’d been removed.
Why?
They’d probably worn out. They don’t last forever. It’s a very intricate system of bearings, balances, and lubricants. They have to be cared for. That’s why a good many airmen dispense with them. The radio-compass requires far less maintenance. And the magnetic compass, of course, requires virtually none. I mean it’s basically a simple Boy Scout compass. It has no machinery. As long as the needle is free to move on its pivot, it works. The only thing that can louse it up is rust. But a gyrocompass is a different animal-fragile, delicate, built to extremely precise tolerances.
Then what advantages would it offer anyone?
It offers accuracy, in those regions where there aren’t a large number of ground beacons in the radio navigation network. And a gyrocompass isn’t affected by such things as electrical discharges in storms-factors which can deflect radiocompasses and even magnetic compasses. Private planes use gyros because they often fly solo without radio beams-visual flight regulations, that’s called. They don’t want to be bothered with all the machinery of radio equipment. And of course the radiocompasses and LORANs are vastly more expensive than the gyros. But in most situations they’re also vastly more useful.
What, exactly, is a gyrocompass? How does it differ from the others?
It’s a balancing wheel. It works on the principle of inertia. It’s set to spinning at a high rate. Like a top, it keeps its balance and resists being pushed off-balance. It rotates within a sphere filled with fluid, or a complex system of bearings and pivots. Regardless of the attitude of the airplane, the attitude of the gyro remains the same with relation to the ground. It’s divorced from all forces outside the airplane itself, except-to some extent-the force of gravity. But it’s not affected by magnetic deposits in the earth, by electric charges in the atmosphere, or by freak deflections of radio beams-which sometimes happen in certain weather systems. It’s rather like a weightless, frictionless objection suspended in the middle of the cockpit. You can point your plane up, down, forward, backward or sideways, or even upside down. The gyro remains in the same position-relative to the ground-at all times, regardless of the position of the airplane that contains it.