than 3 cubic centimeters of lead we have found the airline was forced into the situation. One airline, prior to the Korean incident, attempted to procure 3 cubic centimeter fuel from west-coast suppliers, but was told that it might be obtainable at a prohibitive increase in price of 5 cents per gallon, which was simply the fuel company's way of saying "No".

With respect to item (3), the average lead content used by the airlines prior to PAD Order No. 4 was stated by the PAD to be approximately 3.5 cubic centimeters. We believe that this value is on the high side as reported by the CAA However, we do not have sufficient data to argue this point further. It appears to us that the difference between the PAD and the CAA figures is that the PAD figures were based upon total domestic consumption of aviation gasoline while the CAA figures were based on fuel actually used by the scheduled airlines.

The detrimental effects of lead on engine operation are well known and, as previously stated, we are attempting to obtain quantitative data to show such effects. The adverse effect on safety of decreased engine reliability is a very serious matter as far as the public is concerned, and every effort should be made by the Government to alleviate the shortage of aviation fuel by all other methods before commercial aviation fuel becomes affected.

Sincerely yours,

MILTON W. ARNOLD, Vice President, Operations and Engineering.

NATIONAL AIRLINES, INC.,
March 10, 1952.

Hon. DONALD W. NYROP,

Chairman, Civil Aeronautics Board,

Washington 25, D. C.

DEAR MR. NYROP: This is in reply to your letter of February 28 relative to the Petroleum Administration for Defense Order No. 4.

For your information, following is a description of the difficulties we have experienced since the introduction of higher lead content in our aviation fuel. The over-all picture is probably best shown from the premature engine removal rate. Our DC-4 premature engine removal rate for the period January 1, to October 31, 1951 was 0.36 engine per 1,000 hours of operation. For the period of November 1, 1951, to February 29, 1952 the rate was 0.60 engine per 1,000 hours which represents an increase of 66% percent. Our DC-6 premature engine removal rate for the period January 1, to October 31, 1951, was 0.61 per 1,000 hours of operation. For the period of November 1, 1951, to February 29, 1952, the rate was 1.34 per 1,000 hours which represents an increase of 119.5 percent.

Although the above figures show an alarming increase with the advent of increased lead content in our aviation fuel, one could rightly say that the increase may have been from some other cause which occurred at the same time. How ever, combustion chamber distress is probably the one place where the effects of lead are most pronounced. The following figures speak for themselves.

1 Since Feb. 16, 1952, there have been 2 or more premature cylinder removals for cracked heads on DC4 engines which would bring the premature removal rate for that cause up to approximately 0.115 per 1,000 hours or an increase of 747 percent.

It is apparent from the above figures that combustion chamber distress has increased considerably and when this increase is compared to that of the whole engine, it is evident that troubles from causes other than combustion chamber distress have decreased, otherwise the premature engine renoval rate would have been much higher.

We have instituted a number of changes to combat this effect. Probably the best way to present the changes we have made is to present the recommendations set forth in Aviation Safety Release No. 355 and then show the action taken.

"(a) (Cruise with warm (60° to 75° F.) carburetor air and maintain cylinder head temperatures to the high side." With the DC-6 our problem is to keep the engines cool enough especially as we believe that higher cylinder head temperatures and/or carburetor air temperatures are highly conducive to detonation on this engine. The DC-4 engine is exactly the opposite and we have difficulty keeping it warm enough. This is a problem we have had with us for years and, in order to have better control, we have a test program set up with region 2 of the Civil Aeronautics Administration wherein we propose to permanently close two or more cowl flaps provided we can meet the METO power cooling requirements. Using higher carburetor air temperatures is now under consideration for the DC-4.

"(b) Avoid extremely lean operation." We use best power F/A for cruise on our DC-6 engines and have been doing so for nearly 3 years. Our DC-4 engines operate at very lean fuel/air ratios but at 37° spark timing which we believe will counteract the effect of the lean F/A.

"(c) Remove and clean or renew spark plugs more frequently." We have reduced our spark-plug removal period from 500 hours to 400 hours and have a further reduction to 300 hours under consideration. We have instituted a practice of using only new plugs in our DC-6 engines.

"(d) Periodically exercise exhaust valves while supplying penetrating oil or 'upper lube' to the valve stem or supply such oil to the air inlet when the engine is idling. Such practice may offer some relief from sticking valves." We believe the extra man-hours expended to carry out the above procedure far outweigh the slight benefit that may be derived, therefore, we do not propose to begin this practice.

"(e) Periodic cylinder top overhauling may be necessary between major overhauls in order to forestall chronic failures of the pistons and valve components." We are at present top overhauling any engine on which it becomes necessary to remove two or more cylinders with combustion chamber distress if the engine has a T. S. O. of 1,100 hours or less. In addition to this we have limited all DC-6 cylinders to a total of 3,000 hours.

"(f) Periodic wheeze checking is suggested. "Compression checking, while more involved, is recommended as a more thorough and more valuable inspection." For nearly 3 years we have been performing periodic compression checks on the R-2800-CA15 engines as well as making compression checks at any time when engine roughness is suspected of being caused by leaking valves. In addition to all of the above we have reduced cruise power 5 percent on the DC-4 and 5.5 percent on the DC-6 as of February 15, 1952. In brake horsepower, the DC-4 maximum cruise power has been reduced from 720 brake horsepower to 660 brake horsepower, the DC-6 from 1,200 brake horsepower low blower to 1,100 brake horsepower low blower and from 1,100 brake horsepower high blower to 1,000 brake horsepower high blower.

The lead content of our fuel is stated by our supplier to have increased from an average of 2.97 ml. to 3.96 ml. An anaylsis of fuel drawn from one of our aircraft shows a lead content of 3.98 ml.

Very truly yours,

NATIONAL AIRLINES, INC.,
G. T. BAKER, President.

MUNITIONS BOARD,

Washington 25, D. C., April 11, 1952.

DEAR MR. BECKWORTH: This is in further reply to your letter of March 4, 1952, concerning the tetraethyl lead (TEL) content of aviation gasoline and the effects thereof on engine performance.

The military specification for aviation gasoline allowing a maximum of 4.6 cubic centimeters of TEL per gallon has been in effect since 1943. Actual deliveries of such aviation gasoline to the military during the years 1950 to 1952 have had TEL content, generally, as follows:

Military grade 100/130.-Approximately 95 percent has had TEL content of from 4.0 to 4.6 cubic centimeters per gallon, of which over 60 percent has had TEL content of from 4.5 to 4.6 cubic centimeters per gallon.

Military grade 115/145.-100 percent of this grade has had TEL content of from 4.0 to 4.6 cubic centimeters per gallon of which 80 to 95 percent contained TEL between 4.5 and 4.6 cubic centimeters per gallon.

Air transport activities of the Department of Defense have had no experience in the use of a low TEL content fuel and thus no data are available on which to base conclusions as to the relative performance characteristics of high TEL content versus low TEL content fuels. Recognizing the need for maximum availability of aviation gasoline, the Department of Defense has made no effort to use lower lead content fuels.

To minimize lead fouling problems, several channels of approach have been followed. For example, operational instructions have been issued by the Military Air Transport Service (MATS) whereby under normal cruise conditions the engine primer will be employed for 1 minute each hour to clear the plugs as a preventative measure. Spark plug fouling in flight can be identified by torque fluctuation, rough engine, and backfiring. Where trouble is indicated, the engine primer is applied a second or third time. If the condition is not improved after approximately three attempts, it is considered indicative that the trouble is something other than spark plugs or that plugs are fouled beyond the point of recovery by "inflight" techniques.

Further, continuing studies are being made of improved types of spark plugs and high-frequency ignition systems as possible aids in reducing or eliminating spark plug fouling due to lead deposition.

Finally, the military have been conducting evaluation studies of various types of lead scavenger agents during the past 3 years. Tests containing these special fuel additives are progressing satisfactorily and, in one instance, the use of a new scavenger agent resulted in a 90 percent reduction in spark plug fouling and unscheduled spark plug removal rate. Another series of tests is now in progress to evaluate the effect of a slightly modified blend of the additive in minimizing spark plug fouling without causing any other adverse effects in the aircraft engines.

It is hoped that the above information will prove adequate. We shall be happy to furnish any additional information you may require.

Sincerely yours,

ALFRED H. JOHNSON.

Brigadier General, United States Air Force,
Chief, Office of Petroleum Programs.

Hon. LINDLEY BECKWORTH,

House of Representatives.

DEPARTMENT OF THE INTERIOR,

OFFICE OF THE SECRETARY,

Washington 25, D. C., March 3, 1952.

MY DEAR MR. WOLVERTON: You wrote to Mr. Bruce K. Brown on February 20, 1952, regarding the quality of fuels used by civil airlines, and again to me on February 23, 1952, requesting further information and various documents relating to PAD Orders No. 3 and 4. We are pleased to give you in this reply the information requested in both communications. Copies of the orders are attached as exhibit A.

You are no doubt aware that the Petroleum Administration for Defense does not assume responsibility for the quality of aircraft fuels delivered to the consumers. Purchase specifications for civil aircraft fuels, like other petroleum products, are normally determined between the supplier and purchaser, which, in this case, would be the airline operators. During the first few years following World War II, there were several changes made in both military and commercial aircraft fuel specifications. This, of course, was the first time that any substantial quantities of grade 100 and higher octane fuels were used by commercial operators. They had previously used 91 octane fuel. In general. these changes were directed toward obtaining improved performance, and especially in the case of commercial fuels toward lower engine maintenance costs. During this period, various forces were at work, and different groups, including the airline operators, engine builders, oil refiners, Government agencies, and others became involved to varying degrees in changing commercial aircraft

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fuel specifications. Over a period of time, certain elements of these specifications, such as maximum tetraethyl lead content, were established at a level dictated by competition among the petroleum refiners for airline business. This resulted in a situation in which some airlines used exclusively 3.0 ml. maximum tetraethyl lead per gallon while others used 4.0 ml., or a combination of 4.0 and 3.0 ml. maximum, according to the origin of the flights. Apparently, airlines using 4.0 ml. tetraethyl lead did not consider that the increased maintenance or any of the other factors involved justified the use of the lower tetraethyl lead content fuel.

With the exception of maximum permissible tetraethyl lead content, specifications have generally become standardized for all commercial contracts. The American Society for Testing Materials, which is the recognized authority on standards for petroleum products, issued a tentative specification for aviation gasolines in 1947, ASTM Designation: D910-51T, Revised 1948 and 1950, 1951. This specification covers grades 91/98, 100/130, and 115/145. These specifications, modified to fit specific needs, are now in general use throughout the industry, and with the exception of the maximum permissible tetraethyl lead content for grades 91/98 and 100/130, are the equivalent of current military fuel specifications. A copy of the ASTM specification, exhibit B, is attached for your ready reference.

Fuels of the type used in the above specification, but containing a uniform tetraethyl lead content of 4.01 ml, per gallon, are now used for commercial operations at all airports throughout this country. For this reasons, we believe that neither the fuel composition, which is manufactured to meet specifications, nor the tetraethyl lead content of the fuels can have any effects which would be peculiar to the recent tragedies at Elizabeth, N. J.

The above discussion provides a brief general outline of the evolution of present day commercial aircraft fuel specifications. However, in addition to these grade specifications developed between the supplier and the consumer, certain minimum quality specifications for use in a particular aircraft are established by the Civil Aeronautics Administration. Briefly, the CAA sets up a minimum octane rating fuel for use in an aircraft engine based upon the minimum octane for which the particular type engine was designed and satisfactorily tested. Higher octane fuels are, of course, permissible. The airplane is conspicuously marked to indicate the minimum grade of fuel which may be used, and it is the responsibility of the supplier and the purchaser to see that the proper fuel is delivered to the airplane.

We are sure that the CAA would be glad to furnish you with details of their regulations regarding the quality of fuels which may be used by the airlines. The Petroleum Administration for Defense is the Government agency responsible for the supplies of aviation fuel for the military and essential civilian uses. We, therefore, are obliged, in the discharge of these duties, to investigate all possible courses of action. It naturally follows that, when emergency shortages arise, any arbitrarily established specifications which restrict supplies must come under careful review.

The over-all supply and demand situation is periodically reviewed by PAD to determine the magnitude of additional production required. As of October 1, 1951, increased demands on the part of the military and the loss of 18,000 barrels per day of grade 100/130 from the Abadan Refinery in Iran resulted in an estimated shortage in the world-wide supply of high octane number aviation gasoline of 24,000 barrels per day. Inasmuch as approximately 90 percent of the high octane aviation gasoline production facilities in operation are in the United States, this country was called upon to fulfill that requirement normally satisfied by Abadan production. The majority of the product from that source went to commercial operations carried on by friendly foreign countries overseas and by the American airline operators in foreign areas. Actually, the loss of Abadan production dated back to late June, but operations were continued in foreign areas largely through depletion of stocks in storage. However, certain airline operations, particularly in the Far East, had been drastically reduced. Until last October, it had been possible to provide adequate supplies of fuels by means of well-established procedures and without using allocation powers. On October 19, 1951, the Petroleum Administration for Defense issued PAD Order No. 4, placing a floor on the lead content of commercial aviation gasoline delivered for domestic consumption at 4.0 ml. per gallon and for export at 4.6 ml. per gallon. This action was taken to overcome a significant portion of the shortage of high, octane number aviation gasoline mentioned above.

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In order to obtain additional supplies of aviation gasoline, the Petroleum Administration, at the same time, also issued PAD Order No. 3. This order required that alkylate and all other key blending components of a similar type required in the manufacture of high octane number aviation gasoline be reserved strictly for that use and required the use of all available raw materials for the production of alkylate, as directed by PAD, in order to insure maximum production of that vital aviation gasoline component.

The possibilities of placing a floor on the lead content of commercial aviation gasoline had been discussed with representatives of the airlines and their industry associations in the fall of 1950, when a shortage of somewhat lower magnitude was being faced. They presented, at that time, their objections to increasing the lead content of the fuel that they use to the military specification of 4.6 ml. per gallon. These were carefully considered. At that time, other means (which are still practiced) were available to increase production of aviation gasoline, and it was not necessary to take action in increasing TEL content. Copies of pertinent correspondence, including the requested transcript from the meeting of the National Petroleum Council on September 28, 1950, are attached as exhibit C.

The main objections which airline operators have to higher tetraethyl lead content arises from the fact that the addition of tetraethyl lead to motor fuels causes increased engine deposits. This is true for automotive as well as aircraft engines. Tetraethyl lead is a compound of lead and hydrocarbons which is vaporized or injected along with the fuel into the cylinders of the engine for the purpose of suppressing knock. Modern high output automotive and aircraft engines would not be operable with available fuels without the addition of tetraethyl lead. The fluid used contains scavenging agents which materially reduce but do not entirely eliminate engine deposits. The effect of these deposits must be offset by adequate engine maintenance practices, which, in the case of increased tetraethyl lead, generally means more frequent overhauls.

The use of high tetraethyl lead content fuels is not new. During World War II, all high octane military and commercial aircraft fuels contained 4.6 cubic centimeters TEL. With this TEL content, it was possible to meet the requirements of aviation fuels with limited supplies of alkylate. After the war, with large producing capacity for alkylate available, it was possible to replace a portion of the tetraethyl lead in commercial fuels with alkylate, and this actually occurred in many instances as previously pointed out. The main point here is that with the present type engines, we could never completely eliminate the use of tetraethyl lead, and that even though alkylate were not in short supply, it would be necessary to continue to use some tetraethyl lead in order to produce fuels which would perform satisfactorily. This, of course, means that we are discussing a degree of a situation, rather than any specific principle, and that, in any case, there exists the problem of deposits in engines as a possible result of tetraethyl lead.

Our position, when PAD Order No. 4 was issued in October 1951, was not arbitrary. The reports submitted to the Petroleum Administration during the previous year had shown that approximately 50 percent of the commercial airline operations in this country were then being conducted on fuel containing 4.0 ml. tetraethyl lead per gallon compared to 3.0 ml. for most of the remaining operations. A large portion of these operations was on the west coast, where the overall supply situation on aviation gasoline had been very tight and had forced individual refiners to supply higher lead content fuels in order to satisfy demand. This fact was discussed with the Civil Aeronautics Administration and Civil Aeronautics Board, and there were no data forthcoming from those agencies to indicate that any extraordinary operating problems were being encountered in that area from the use of 4.0 ml. tetraethyl lead fluid. This connotes that the Pacific airlift, as well as all commercial operations in that area, had been operating satisfactorily on fuel containing the higher lead content for at least a year.

In addition to the long standing use of considerable quantities of 4.0 ml. fuel in domestic commercial operations, at the time PAD Order No. 4 was introduced, approximately half of the aviation gasoline for export in the fourth quarter for commercial use in foreign areas was scheduled to contain 4.6 ml. of tetraethyl lead. In this connection, PAD has been informally advised by the military services, the high octane aviation gasoline of which specifies 4.6 ml. tetraethyl lead per gallon, that they never had an accident where tetraethyl lead was found to be a significant factor.