~ Archive for April 16, 2003 ~

Staying Alive in Small Airplanes

13

One of the hazards of wealth and/or hanging around with rich people is the possibility of dying in a small airplane crash.  If you’re an average schmoe you’ll wear a rut in the pavement between house and job, be entertained watching TV on the sofa, watch your kids get on the schoolbus every day, and drop dead of obesity [should say “average American”, I guess] at age 83.4.  The rich, however, must shuttle among their 5 luxury homes and get their kids to and from exclusive private schools in the countryside.  Shuttling requires many private airplane flights, not least because the luxury homes may be on islands where airplanes provide the only access.  If you want to escape the rabble you have to go somewhere that is impractical to read by car and that isn’t so populated that it merits daily Boeing 747 flights.


A couple of recent airplane crashes, however, have got people scared.  One involved Minnesota Senator Paul Wellstone and an April 4 crash here in Massachusetts involved M. Anthony Fisher, a real estate tycoon from New York.  Both were in Beech King Air airplanes, each of which had two engines and two professional pilots.  Both were doing non-precision instrument approaches in bad weather.  In both cases people initially suspected icing, a terrifying flight hazard in cold-weather clouds but one that the King Airs are reasonably well-equipped to handle.  In both cases the actual cause appears to have been that the airplane was simply flown too slowly and fell out of the sky, which is by far the most common way to crash an airplane for all levels of pilot.  People fear engine failure but they die from pulling the stick back too far.


Let’s start by looking at the most recent crash, which involved Bob Monaco, a pilot based from our local airport (Hanscom Field in Bedford, Massachusetts, BED).  Today’s Boston Globe carries a story that is typical for (a) being filled with errors, and (b) not providing the URL where readers could find the original National Transportation Safety Board report and study it themselves.


The goal of the trip was to fly the rich family up to a prep school that the daughter was considering attending, then take the rest of the family and its interior designers out to their house on Martha’s Vineyard.  The pilot, Bob Monaco, planned the flight initially from New York to Bedford, a large civil/military airport with a 7000-foot main runway and an instrument landing system (ILS). 


Background on aerodynamics:  Airplanes hold themselves up by pushing air down.  In flight, an airplane’s wings are angled up. As the plane moves forward this angled surface pushes air downward and, as a reaction, the airplane rises up (Newton’s 3rd Law). Air weighs a lot less than the metals and plastics in the airplane and therefore one must push a lot of air down in order to pull the plane up, which is why wings are so physically large.  An airplane must maintain a reasonably high forward speed for the wing to do its job; a wing that isn’t moving pushes no air down.  If a pilot, in attempting to slow down for landing, slows down too much the plane will “stall” and become hard to control.  If the pilot does not immediately push the stick forward to pitch the airplane down and pick up more speed, the plane may go into a “spin” and start to fall out of the sky.  A plane can be recovered from a spin but usually this requires more altitude than is available if the spin happens while approaching to land.  Turning an airplane uses up lift that would otherwise be available to hold altitude and therefore an airspeed that works for level flight will result in a stall in a tight turn.


Background on flying in the clouds:  An ILS approach is referred to as a “precision approach”.  Under normal circumstances the Air Traffic Controllers (ATC) give you radar vectors and altitudes to fly until you intercept the radio beams of the ILS.  They are required by regulation to set you up so that you need not make more than a 30-degree turn to get onto the ILS, i.e., ATC points your airplane more or less straight in toward the landing runway.  Once established on the ILS you make very small adjustments in pitch and bank to keep the needles centered and set the engine power so that your airplane holds a slow steady speed (pointing the nose down toward the ground would normally build up a lot of speed so you cut engine power from its cruise setting to reduce the total amount of energy being put into the system).  Notice that at no time on an ILS is the airplane required to make a turn; the airplane is going slow but flying straight.


At Bedford the ILS 29 approach lets you go down to 300′ above the ground without seeing anything, then, if you can see the runway lights you’re allowed to go down until you’re just 100′ above the ground.  In an emergency you wouldn’t worry about ever seeing the runway but keep flying the needles until the wheels slammed down on the pavement (they do this in training in Europe, actually).


Not only does an ILS provide low minimums but it also generally comes with assistance from ATC.  If you’ve somehow gotten very confused or your equipment isn’t working right and you’re off-course or at the wrong altitude, they’ll probably call you on the radio (they are invariably polite and ask you to “say altitude” or “say position”, hoping that you’ll discover your mistake, rather than “you’re in the wrong place, bozo”).


A non-precision approach is a much more complex procedure that (a) requires a bunch of turns in the clouds, fairly slow and low to the ground, (b) makes the pilot(s) solely responsible for the airplane’s position, and (c) requires the airplane to stay at a higher altitude if the pilot cannot see the runway.


Why would you ever do a non-precision approach?  For the airlines the answer is generally that you don’t.  You fly from ILS-equipped airport to ILS-equipped airport.  If there is no ILS at an airport that you wish to serve, you twist the government’s arm into installing one.


On April 4, Bob Monaco changed his plan, while in flight, to go from an ILS-equipped airport (BED) to a much smaller airport, Fitchburg (FIT) at which only non-precision approaches are available.  Because he is dead we can’t ask him why but we can presume that he got a weather report for FIT that said the clouds weren’t that low and FIT was closer to the prep school, thus saving 45 minutes of driving.


From the NTSB report, it sounds as though the clouds were right around 1000′ above ground level, which is the minimum height that Monaco was required to maintain above the runway until he could see it.  It sounds from the witness reports that he did not really see the runway until he was right on top of it.  At this point he was too high to land.  However, it is legal, assuming that you can maintain continuous visual contact with the runway, to make tight circles around the airport and then land, perhaps on a different runway than the one you were initially approaching.  You want the circles tight so that you don’t risk flying into more clouds.  Note that tight circles imply turns and that if you are hoping to land an airplane you want to be going slowly.  Recall from the aerodynamics paragraph above that turning makes it more likely that the airplane will stall at a given speed.


Even with two pilots on board, the challenge of keeping the runway in sight, setting the plane up for landing, and making those tight turns was apparently too great and the King Air crashed.  The NTSB report says that the airspeed indicators showed 60 and 66 knots on impact, which is a good speed for a little training airplane but much too slow for a King Air in a turn (the King Air’s typical approach speed is 100 knots).


If you’re planning to take a trip in a small airplane, what lessons can you learn from these mournful events?  First, legal does not equal safe.  One reason that the airlines have such a good safety record is that they are much more conservative than required.  For example, many airlines have found that their pilots are unable to maintain acceptable tolerances during circling-to-land approaches such as the one Bob Monaco was attempting and therefore they no longer train pilots on this procedure nor use it in operations.  Second, an ILS greatly enhances safety.  If the weather is marginal and your friend says “we’re going to the little airport at Gaithersburg, Maryland” repond with “I don’t mind driving an extra 20 minutes from Dulles or Baltimore-Washington International”.  Third, if you really want to be safe wait for the weather to improve.  Even with the best equipment and pilots, sunshine adds a big safety margin.

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