Progress, of a sort

08403v hanno, originally uploaded by A30yoyo.

Professor Karl D. Stephan, author of the Engineering Ethics Blog, shares an interesting observation while reviewing Air Accident Investigation (3rd edition, 2006) by Mr. David Owen.

I was intrigued by a photo of what has to have been one of the largest biplanes ever built, a Handley Page H. P. 42 flown by Imperial Airways in trans-Channel service in the early 1930s. It was about four stories high and had four engines clustered around the fuselage. Owen’s point in including it was that although there were plenty of accidents back then, early commerical aviation was operated so conservatively that in ten years of use, the H. P. 42 never lost a passenger to a fatal accident.

All this changed after World War II, when jet aviation and economic growth transformed the flying public from a few privileged individuals into hordes of airborne bus passengers. Higher speeds and long over-water flights raised the cost of in-flight mechanical failure to the point that surviving a commercial airline crash was a dubious proposition at best.

— Stephan, Karl D.  “Air Accidents in Perspective.” Engineering Ethics Blog, 16 November 2009.

There are a huge number of factors that contribute to increased lethality in crashes of modern jet aircraft.  In addition to increased gross weight, payload, speed, and frequency of over-water flights, there is the nature of the aircraft themselves.

Airports of the day rarely had asphalt or concrete runways, so the H.P. 42 had to be able to operate from semi-prepared grass or dirt airstrips in the middle of nowhere.  Its takeoff ground roll was just over a thousand feet, and its maximum takeoff weight (MTOW) was around 28,000 pounds.

Today’s jet airliners are not capable of operating from 1,200 foot grass strips on a routine basis.  They weigh several times as much as an H.P. 42 (the 737-300’s MTOW is 124,500 lbs), so their takeoff roll is necessarily much longer.  Their gear is not designed to handle operations from rough fields; they need asphalt, concrete, or (with special tires and gear kits) gravel.  Your odds of randomly finding 1000 feet of open grass or dirt in any given spot in Central Europe, Africa or Southern Asia are pretty good compared to your odds of randomly finding 4-5,000 feet of level asphalt or concrete that can also withstand the weight of 125,000 pounds of airliner landing on it.

All that said, jet travel is here to stay, and in spite of the increased risks, it has also grown much safer.  I’d be interested in reading Mr. Owen’s conclusions for myself, so I shall check with the library to see if they have a copy.

SEMI-RELATED: Professor Stephan doesn’t post very often, perhaps once a week at best, but his entries are full of cogent thoughts.  I also enjoyed this post about toxic drywall from China, and what the likely outcome might be for banks and consumers stuck with such toxin-infused homes.  I look forward to reading more.

Category: Aeronautics, Industria  Tags:
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