Press Release, Letter from the President's Special Board of Inquiry on Air Safety to President Harry S. Truman

267 HOLD FOR RELEASE HOLD FOR RELEASE HOLD FOR RELEASE JULY 7, 1947 CONFIDENTIAL: The following third interim report to the President by the President!s Special Board of Inquiry on Air Safety MUST BE HELD IN STRICT CONFIDENCE UNTIL RELEASED. NOTE: Release to all newspapers appearing on the streets NOT EARLIER THAN 6:00 P.M., E.D.T. today, Monday, July 7, 1947. The same hour of release applies to all radio commentators and news broadcasters. PLEASE GUARD AGAINST PREMATURE PUBLICATION OR RADIO ANNOUNCEMENT. CHARLES G. ROSS Secretary to the President "July 7, 1947 My dear Mr. President: TRUMAND NARA Your Special Board of Inquiry on Air Safety herewith tenders you a third interim report. The Special Board has been concerned lately with that type of accident known as collision with terrain. These accidents normally occur at night or under weather conditions when visibility is restricted, These accidents have various causes, some of which cannot be wholly eliminated. But it is possible now to reduce those elements of causation that stem from the inherent fallibility of the aneroid altimeter. Depending as this does on barometric pressure and the accurate conveyance of that pressure to an airplane in motion, errors in recording absolute heights may occur for various reasons, such as temperature, high winds, pressure changes and stoppages in the static tubes. To counteract these, two immediate measures can be taken. They are, in brief, provision for a terrain proximity indicator as a secondary aid and insistence upon more adequate clearance of terrain when barometric variations are likely to occur. The Special Board thus recommends the adoption of two measures. First. That all scheduled transport aircraft be required to install as soon as possible approved absolute terrain proximity indicators operating on electronic principles as a secondary aid to the aneroid altimeters presently required. A number of these secondary aids are now or will shortly be available. Several airlines have already contracted for their installation. The devices are inexpensive and they can be arranged so as not to introduce an additional and confusing burden on cockpit procedures. They should warn pilots of the proximity of terrain at distances both of 2000 feet and 1000 feet, and, for approach purposes, give a similar indication at a predetermined altitude between 300 feet and 500 feet. These devices are not presently fully perfected. But they are satisfactory enough to require their immediate installation as secondary aids. To promote their perfectibility, it is suggested that continuing study in the light of actual experience consequent upon their installation be pursued by the appropriate governmental authorities. If the result be a better device, the recommended secondary aids can be easily scrapped for the newer and better instruments. (OVER)