Technicalities (September 2001)

Peter ruminates on the difficulties of giving away a perfectly good airplane ride.

Each year I donate a flight to Catalina Island to the fundraising silent auction at my daughter's school. Each year somebody buys it for a few hundred dollars. I wish I could say that each year the purchaser is delighted with the trip, but in fact hardly anyone ever actually takes it. I suppose that they bid on it in a haze of Chardonnay-induced optimism, but in the cold light of dawn they begin to imagine themselves dog-paddling in mid-channel, Reeboks full of water, children imminently orphaned, and so on, and so they keep postponing the trip until it fades from memory.

Mindful of this pattern, I described the offer for this year's auction catalog as a flight with "aviation safety maven" P.G., or something of that sort. I figured that having meditated upon countless accidents for Aftermath, I now qualified as some kind of expert. Whoever put together the booklet, however, apparently didn't like my wording and changed it to "aviation safety buff." The word "buff," which seems to me more or less interchangeable with "hobbyist," at once distorted and trivialized my relationship with aviation safety. But then perhaps everyone is a safety buff who is not a death buff.

Despite the goofy wording, someone did pony up $400 for my services. I was still in the middle of trying to persuade last year's buyer that we stood a good chance of getting back from the island alive-she kept glancing down doubtfully at her adorable three-year-old and saying, "Well, I know, but…"-when this year's buyer, a gloriously statuesque woman of Indian extraction, strode confidently up to set a date.

She, her husband, a friend of theirs and mine, and I flew out to the island in a Cherokee Arrow on a Wednesday morning. It was hazy-too hazy for much of the impressive and repellent expanse of Los Angeles to be discerned. We took off from Van Nuys and flew through the "Los Angeles special flight rules area"-or as we who have nervously threaded it for decades prefer to call it, the "corridor"-that transforms L.A.'s Class B airspace, topologically speaking, from a ball into a doughnut. This is one of the high points of the trip; passengers are always astounded to be flying right over the center of Los Angeles International Airport at 3,500 feet while the big jets take off and land incessantly, often several at once, directly beneath them. It gives them the thrill of voyeurism and the sense of committing a criminal act at the same time.

On emerging from the corridor at the south side of LAX, we began a climb, and as a safety buff I felt it was my duty to explain that, in order to be able to glide back to dry land in the event of a power loss, we would ascend to about 5,500 feet by the middle of the channel, which is about 19 miles wide (not the 26 of the old Four Preps' song-Twenty-six miles across the sea, Santa Catalina is a-waitin' for me. The island of romance, romance, blah blah blah, etc…).

I felt the disingenuousness of this explanation as I was giving it. As with most aeronautical enterprises, the devil is in the details. If the engine were to stop running in a sudden and catastrophic way somewhere between the Palos Verdes peninsula-which is a promontory, not a peninsula, by the way-and the island, the Arrow would be hard pressed to glide as much as 9.5 nm from 5,500 feet; and for that matter it might be difficult on a hazy day, if the failure did not occur precisely at mid-channel, to know which way to glide. There are cliffs on both shorelines, and so a desperation forced landing would probably end up in the water anyway; but it would be better to be a hundred yards offshore than several miles. As I learned when I took a course of water survival training preparatory to riding in a Navy jet, I am not that strong a swimmer, especially when fully dressed. For that matter, ditching is a very uncertain enterprise with many hazards of its own. I did not explain any of this to my passengers, who seemed quite unconcerned. What's more, they were right to be unconcerned. The chance that the engine would quit at all, let alone during the tiny slice of time we would spend in the middle of the channel, was infinitesimal-hardly even worth considering.

Dire possibilities having been duly considered despite their extreme unlikelihood, we arrived on the island without incident. I explained before we landed that because of its humped shape the runway gives the impression of ending at what is really mid-field. My passengers, who were in a mood to enjoy everything, exclaimed over the exciting illusion that after touching down we were about to roll off a cliff. When we parked, they were amused that I chocked the airplane with rocks; this seemed to them the height of Crusoesque improvisation.

Catalina has a peculiarly Mediterranean feeling, as I suppose much of southern California does, but it also has something not found in Nice or Cannes: bison, imported by filmmakers in the distant past. Encountering no natural predators, they have multiplied to the point where the island's human occupants have no choice but to eat them and to encourage others to do so. We pitched in, devouring our buffaloburgers on the balmy terrace of the airport restaurant. The menu says that buffalo is exceptionally low in fat and cholesterol. Nevertheless, it tastes perfectly good.

After lunch we took a stroll down the road to inspect a small herd of the beasts at close hand. There were six cows-I suppose-and four light-brown calves. They shuffled about uneasily as we approached, and we, in turn, stopped uneasily. We were close enough to appreciate their great size, but not close enough to see their liquid brown eyes and long eyelashes. I have inspected buffalo eyes at a range of a few feet in Yellowstone, however, and I'm not kidding-they really are beautiful.

I was hoping that the haze would clear a little, but it didn't, and the trip back, except for a scenic swoop along Catalina's north shore, was like the trip over. Still, my guests were ecstatic about the flight; it was wonderful, fabulous, fantastic. And they were evidently sincere, since I heard for days afterwards from third parties at school about the amazing things we had seen and about my own skillful and heroic piloting.

It's odd that this wonderful escape from the banality of everyday routine-simply flying across a short stretch of city and ocean and landing on an island for lunch-seems to so many people like such a terrifying flirtation with death that they are willing to throw away hundreds of dollars rather than risk it. And these same people eat sushi.

More Horsepower Awhile agoafter the press had reported some fanciful figures for the equivalent horsepower of the jet-propelled carlike thing that exceeded the speed of sound-I wrote about the horsepower of various large powerplants, including those of ships, some of which are rated at over 200,000 hp.

I recently received a note from an occasional correspondent, Stephen Slobin, who works at NASA's Jet Propulsion Lab in Pasadena, California. He had visited the Edwards Air Force Base museum and seen one of the X-15's rocket engines. The XLR99 engine, powered by anhydrous ammonia and LOX, Slobin wrote, "was said to have had 57,850 pounds of thrust, equivalent to 600,000 hp. They claimed it was the most powerful aircraft engine ever built."

"Pete Knight set an X-15 speed record in 1967 of Mach 6.72 (4,520 mph, 6,629.3 ft/sec). Doing our standard calculations, 57850 x 6629.3/550 = 697,281 hp, which agrees pretty well. By comparison, a 90,000 pound thrust B-747 engine at 600 mph calculates to be 144,000 hp (107,424 kW), or enough to power 107,000 homes, supposedly, although I do rather like the idea of a fleet of nuclear submarines docked in Los Angeles Harbor with a lot of big power cables running ashore."

The California power crisis does seem to have a lot of people in a lather, but I hadn't heard the nuclear submarine proposal. As far as the 747 is concerned, I think that most 747 engines are rated at something closer to 50,000 pounds thrust. But in any case that's static thrust; when they're cruising at FL 370 their thrust is much lower, and so is their equivalent horsepower.

What makes the XLR99 rocket engine superior in horsepower, if not in thrust, to the 747's turbofans is that, unlike a jet engine, it could deliver its rated thrust at any altitude and any speed. As you can see from Slobin's calculation, converting thrust to horsepower is simply a matter of multiplying by speed and dividing by a constant that depends on the units being used. In the English system-there are no horses in the metric system, their place being taken by watts-speed is conventionally expressed in feet per second and thrust in pounds, and the constant you divide by is 550.

Another correspondent, Jack Kane, took me to task for my careless statement that torque and horsepower tend to be of about the same numerical magnitude. Mea culpa. I was thinking about cars. Using English units, torque and horsepower are, in fact, numerically equal at 5252 rpm-a speed at or around which most auto engines may operate, but not many airplane engines. Since the operating speed of aircraft engines is typically half that number, I should have said that the number of pound-feet of torque is usually about twice the number of horsepower. (The relation between torque and horsepower is a simple one: torque equals horsepower times 5252 divided by rpm, and horsepower equals torque times rpm divided by 5252.)

I had mentioned torque in the context of slipstream effects. Even though the torque is twice what I claimed it was, what I said about it is still true: it's not a big factor in the control and trim of most airplanes. It can be, however, if the engine is big enough and the wingspan is small enough. Think of the GeeBee, the stub-winged, barrel-bodied racer flown by Jimmy Doolittle in the 1930s. According to Doolittle, it was always trying to go over on its back-presumably because its big engine was trying just as hard to spin the airplane one way as it was to spin the prop the other.