4. Number of reported recap failures versus total number of landings was about the same for each airline, suggesting an industrywide problem. 5. Two recap agencies were involved in a relatively large percentage of failures; however, these particular agencies are by far the largest recappers. : With this point in mind, but with no specific figures as to numbers of tires recapped by each agency, there did not appear to be any trend as to manufacturer or recap agency. 6. The 120 cases during the 9-month period investigated indicated the problem was wanting of concerted corrective action. 7. There were several cases of structural damage, although none of serious proportions and no crippling damage to primary structure. It was recognized, however, that a potential hazard existed, such as damage in wheel wells, to control systems, fuel, and hydraulic lines, etc. Since the original study, spot checks of MRR's have been made from time to time. For the period of October 1, 1962, to July 30, 1964, there were 149 failures. This is about a 50-percent reduction over the rate in the earlier study. A recent check reflected 45 tire failures during the second quarter of 1965 and 19 failures in July 1965. This higher rate for July is expected as it follows the trend every year of considerably higher rates during July and August. CORRECTIVE ACTIONS AND RESULTS On October 25, 1962, the preliminary results of the Bureau of Safety study were made known to FAA and a recommendation was made for corrective action. FAA immediately surveyed the operators for inspection techniques and conducted studies of their own. FAA issued notice No. FS 8320.22 on March 7, 1963, calling attention to the improved standards contained in MILR-7726B, and that MIL-C-7726, cited in CAM 18.30-9, was no longer applicable. Other material was issued from time to time, the most notable being notice FS P 8340.1A CH 27 on October 29, 1964, outlining procedures adopted by several carriers to further improve tire reliability. Listed were: (a) Frequent, in depth tire-pressure audits. (An unannounced visit is made to an airport, and every aircraft tire of a particular operator is given a pressure check and an inspection. Complete records of the findings are made and kept for future comparison and reference.) (b) Dial-type pressure gages are used to replace other types. The mechanics are trained to use the dial gage properly. (c) Mechanics are trained in the meaning of usable tolerances together with the effects of under and over inflation. (d) Proper assessment of tire damage, discovered by visual inspection is stressed in the training program. (e) Establish and maintain detailed tire records, including results of tire audits, chronological histories of tires found with discrepancies, types of failures, costs, etc. Establish a periodic evaluation of the records in terms of trends (improvement or deterioration), problems, and possible corrective action. (f) Development of methods to improve attitude toward necessity for proper inflation and to overcome psychological barriers, for example: (1) Placing dial gages in a padded box not only to preserve its accuracy but to also visually impress the user that it is a delicate and important instrument. (2) Keeping the dial gage and the air bottle together on a common cart or wagon with required lines and fitting. (Easy mobility of the cart or wagon is desirable.) (3) Providing tire gage calibration checks at regular and frequent intervals. In addition there has been a continued effort by the carriers, tire manufacturers, and recappers, and the Tire and Rim Society to improve the inspection techniques and more closely define acceptable and unacceptable tire conditions. One cargo carrier has elected to eliminate recapped tires on its jet equipment because of the unique exposure, wordwide, to poorer surfaced runways. Most of the jet carriers have limited high-speed tires to a maximum of six recaps regardless of tire condition. ACCIDENT RECORD Although there have been a considerable number of aircraft tire failures (primarily recaps on jet aircraft), damages of serious proportions have been 54-441-65-16 extremely rare. Most structural damage has been confined to "soft" structure: i.e., fairings, flap surfaces, landing gear doors. A check of U.S. air carrier accident records for the period 1960 to 1963 indicate only two accidents due to tire failure: DOCKET 1-0091 September 13, 1960: Capital Airlines Viscount 700D, Minneapolis, Minn. The aircraft was being rotated for lift-off when the No. 1 main wheel tire recap tread came off, struck the No. 2 propeller, and penetrated the left side of the fuselage. The takeoff was continued and the No. 2 propeller was feathered due to vibration. The flight thereafter returned and landed without further incident. Probable cause: Failure of tire tread during takeoff. DOCKET 1-0057 September 25, 1963: Riddle Curtiss C-46, Orlando, Fla. At 1325 e.s.t., the captain of N-1243N initiated takeoff from the Orlando (Fla.) Airport using runway 7 which is 6,000 feet in length. At the time the runway was wet and light rain was occurring. As full power was established, a pronounced thumping or vibration began; however, the takeoff was continued until the aircraft had accelerated to between 60 and 65 knots, when a severe shaking of the right engine occurred. At this time the takeoff was aborted. Before the aircraft stopped it turned right, and the right main wheel went off the side of the runway. Rapid deceleration occurred and the plane nosed down, hit on the propeller and nose section, and rebounded to a normal three-point position. Investigation revealed the right main wheel tire tube had failed. Examination of the tube revealed it had failed over a section where the tire fits to the wheel and where the thickness of the tube was 0.092 inch as compared to the manufacturer's standards of 0.110, minimum, and 0.180, maxiThe tire casing inside and out was in good condition. mum. Examination of the runway disclosed marks from the right tire over a distance of 588 feet short of the final stopping point of the aircraft. Heavy braking marks from the left main tire were evidenced over a distance of 364 feet prior to the final resting place of the plane. Probable cause: Failure of the defective right main tire tube during the takeoff roll, resulting in a loss of directional control. The air carrier accident summaries for 1964 have also been checked and no accidents were attributed to tire failures. GENERAL COMMENTS Aircraft tires, particularly recapped high-speed tires, continue to be a maintenance problem with the airlines; however, concerted efforts have reduced the frequency of failures. Continued surveillance and improvement in the state of the art should reduce the frequency even more. Tire failures do not appear to be creating dangerous situations although there is, as with any component failure. the remote possibility of such failures leading to further complicated situations. Based on the latest quarterly figures available on tire failures (April, May, June 1965), i.e., 45 failures versus approximately 960,000 operations (takeoff plus landing), the current failure rate is 1 failure per 21,300 operations. In 1962 the rate was about 1 in 9,000 operations. The 2 accidents in the 5-year period 196064 against an approximate total number of operations of 18 million gives an accident rate of 1 in 9 million operations. Statistically, at least, the odds of causing injury are nil. No effort should be made to extrapolate the aircraft tire situation to automobile tires for the following reasons: 1. Aircraft and automobile tires are subjected to different conditions of loading, wearing, etc. The major loadings given to aircraft tires are landing loads; i.e., spin-up from zero rotation to rotation compatible with landing speed, and the impact load of being dropped from several inches to several feet at speeds of 100 to 150 knots. 2. Aircraft tires are multiply construction. For example, high-speed tires are 16 or more ply compared to 2 and 4 ply of automobile tires. 3. Side stresses are generally lower on aircraft tires and they are not subjected to curb strikes and pressures against sidewalls. 4. Aircraft tires are generally free of subjection to nails, beer cans, glass, chuck holes, etc., which automobile tires come in contact with almost daily. 5. Aircraft tires are not subjected to misalinement conditions as the front tires of an automobile are, nor are they involved in power transmission as the rear automobile tires are. 6. The multiwheeled axle and bogie systems of aircraft offer a redundancy not found on automobiles (heavy duty trucks have this redundancy on rear axles). JOHN S. LEAK, Chief, Technical Services Section. COMMITTEE ON LABOR AND PUBLIC WELFARE, Hon. WARREN G. MAGNUSON, U.S. SENATE, July 12, 1965. DEAR SENATOR MAGNUSON: As you may recall, on June 7 I wrote to the major automobile manufacturers asking them a series of questions on automobile tire safety. The presidents of the four major manufacturers, or their designated representatives, have now replied to my letter. I am forwarding their replies to be included in the hearing record of the Senate Commerce Committee. The committee has been taking testimony and gathering evidence on bill S. 1643. At this time I want to comment on these letters and ask that my comments also appear in the record. I want to express my appreciation to the automobile industry for the prompt and thorough replies given to my questions. I am sure that the industry is sincerely interested in automobile safety. However, testimony at the Federal Trade Commission hearings and the statements of the auto manufacturers in their letters to me make its abundantly clear that large numbers of new automobiles are equipped with inadequate and dangerously unsafe tires. For this situation the auto manufacturers are solely responsible because they decide what quality tire shall be placed on the car. It is scandalous to equip new automobiles with tires that are unsafe when the car is fully loaded. The automobile industry is well aware of the inadequacy or their original equipment tires and apparently does not intend to do anything about it. I think, therefore, that Federal legislation setting safety requirements for original-equipment tires is necessary and fully justified. The main question which I asked the automobile manufacturers was whether the tires supplied on their cars were adequate for full-load service. At the Federal Trade Commission hearings, in January, there was expert testimony to the effect that these tires were not adequate. The replies from the automobile company presidents confirmed this fact. Although they contend that their tires are adequate, all of the auto companies attach special conditions which, in my opinion, are both unrealistic and in some cases dangerous. All of the auto manufacturers state that the tires on their cars must be overinflated in order to accommodate what I consider perfectly normal loads, such as six passengers plus normal luggage in a six-passenger sedan. American Motors, for instance, states that if the tires on its cars are overinflated as American Motors recommends, they should be "adequate for occasional full-load service." This is a shocking admission which should jolt everyone concerned about the death of 47,000 Americans a year on our highways. The Ford Motor Co. states that its large station wagons, commonly referred to as "nine passenger," can carry a full load up to 1,300 pounds only if the rear tires are inflated to 36 pounds pressure. General Motors recommends increasing the tire pressure in sedans from 24 to 30 pounds to accommodate full loads. For loads of 1,200 pounds in station wagons (which are common), General Motors recommends optional oversize or eight-ply-rated tires, while supplying a two-ply, four-ply-rated tires as standard equipment. These letters add up to a clear admission that the tires supplied with new cars not not adequate for all around use unless each individual motorist carries out an elaborate ritual of weight computation and inflation and deflation. I seriously doubt that more than a tiny minority of American motorists would ever be expected to follow these elaborate precautions, calculating the weight of car passengers and accessories with great precision and changing tire pressure to accommodate it. Furthermore, the attempt by the automobile manufacturers to make inadequate tires adequate by overinflating them creates serious dangerous in itself. I asked an official of the Tire & Rim Association to comment on the Ford recommendation of tire pressures up to 36 pounds. He stated that it was the consensus of the industry that such a tire pressure was dangerous, that it was likely to cause extremely rapid wear, and would increase the danger of blow-outs. The auto company replies also show that there was a shockingly low margin of safety in the tires supplied with new cars. If you read the manuals, General Motors advises you to increase your front tire pressure if you add air conditioning. Mercury recommends a much larger with the use of air conditioning. It seems doubtful that air-conditioning equipment would weigh as much as a single passenger. Yet the industry seems to be telling us that the addition of this one accessory pushes the car so far beyond the margin of safety that the tires are no longer adequate. No amount of evasiveness or talk about inflation and deflation will meet this problem. It is obvious that higher quality tires, with much greater safety margins, are required on our automobiles. The auto company replies point up much better than anything I could say the existence of a national scandal in automobile tires. Tens of thousands of American motorists, fooled into thinking they are safe in their shiny new cars, are speeding across the Nation on a time bomb which could explode at any time. Unfortunately, I do not believe we can leave the protection of the public interest in tire safety up to the fiercely competitive automobile industry. We have got to set some standards for tires at the national level. I would appreciate it if the enclosed replies from the automobile manufacturers could be included in the record of the hearings, along with my covering letter. Sincerely yours, GAYLORD NELSON, U.S. Senator. AUGUST 20, 1965. Mr. JAMES SEARS, Rubber Manufacturers Association, DEAR MR. SEARS: I am enclosing a copy of a letter which was sent, at Senator Hartke's request to the automobile manufacturers, requesting their comments on the relative safety of nylon and rayon tires. The committee would similarly appreciate any light which the rubber manufacturers can shed on this issue. Sincerely yours, Mr. MICHAEL PERTSCHUK, MICHAEL PERTSCHUK, Staff Counsel. RUBBER MANUFACTURERS ASSOCIATION, Staff Counsel, Committee on Commerce, Washington, D.C. DEAR MR. PERTSCHUK: This is in response to your letter of August 20, 1965, asking whether the RMA wished to comment on the relative safety of nylon and rayon tires. This inquiry was discussed at a meeting of the RMA Tire Engineering Committee held on September 22, 1965. It is the view of our committee that a tire can be made adequately safe whether made of rayon or nylon. It is the responsibility of the tire manufacturer to put the quality of the cord-whether rayon or nylon-into the finished product for safe performance. It is true that differences exist in the physical properties of the various cords that are being used and may be used in the future in tire constructionwhether they be rayon, nylon, polyester, or others. However, the amount and kind of cord and the cord angle used in tire construction are only two of several elements affecting the ultimate safety and performance of the product. Equally important factors include the various rubber compounds used in the tread stock, sidewalls, and in the adhesives used on the cords; design as it affects tire profile and the "footprint," or the tread area placed on the road surface; and even tread configuration. It is the art of bringing all elements into proper balance, the engineering compromise, that gives a tire its varied properties of safety, endurance, ride, good cornering, and responsive braking characteristics. Sincerely, Hon. VANCE HARTKE, W. J. SEARS, L. B. STEWART MEMORIAL FUNERAL HOME, DEAR SENATOR HARTKE: The Louisville Times of August 13, 1965, carried a story concerning the hearings before the Commerce Committee on the proposed bill to establish higher minimum standards on factory-installed tires on new cars. Representatives of the Automobile Manufacturers Association, General Motors, Ford Motors, and American Motors are quoted as saying that present factoryinstalled tires are safe and that there is no need for legislation on this matter. I disagree completely with their statements. In connection with our funeral home we operate two ambulances, a Cadillac and an Oldsmobile Ninety-Eight. In less than 2 years we have thrown the tread off of four factory-installed tires. Because of past experiences we are overinflating these tires but this has not solved our problems. One tire recently failed while transporting a critically ill child to the children's hospital in Louisville and had it not been for our State police escort, who took the child on to the hospital, it is possible the child would have died before we could change tires and get there. Because of the rate of speed involved in this case it is perhaps understandable that this tire could fail; however most of our failures have occurred at legal turnpike speeds on Interstate 165. From the experience of tire manufacturers at our Indianapolis 500, we know that tires have been developed which will operate safely at high speeds. It would seem to me to be almost criminal for an automobile manufacturer to place on a chassis to be used for an ambulance anything less than the very best tire available for the purpose. I would urge your support of legislation to remedy this dangerous situation. Yours sincerely, CHARLES M. STEWART. WISCONSIN RURAL LETTER CARRIERS' ASSOCIATION, Hon. WARREN G. MAGNUSON, Chairman, Commerce Committee, U.S. Senate, June 18, 1965. DEAR SENATOR MAGNUSON: At the annual convention of the Wisconsin Rural Letter Carriers' Association held in La Crosse, Wis., this week, the attached resolution was passed without dissent. |