Foreign Relations of the United States, 1964–1968, Volume XXVIII, Laos

326. Memorandum From the Chairman of the Joint Chiefs of Staff (Wheeler) to Secretary of Defense McNamara¹

CM-2876–68

Washington, January 2, 1968.

SUBJECT

• Use of Propeller and Jet Aircraft in Laos

1. Reference is made to your memorandum, dated 18 December 1967, subject as above.²

2. Findings of the study forwarded by the reference state that the effectiveness of the propeller aircraft in Laos over that of the jet is significant; and, based thereon, it appears possible to substitute two A–1 squadrons for two F–4 squadrons in Thailand.

3. On the basis of a review of the study, it appears that use of propeller aircraft against a specific target—trucks—is more effective than the jet type aircraft in the relatively permissive air defense environment of Laos. However, our present force posture in Thailand was based on the fact that these forces would be primarily assigned to targets in North Vietnam (NVN), with Laotian targets as their secondary mission. During good weather periods in NVN the maximum number of Thailand based aircraft is required for strikes in NVN. As a bonus effect, this capability is used to provide a maximum number of sorties in Laos during bad weather periods in NVN. Accordingly, the replacement of two F–4 squadrons by two A–1 squadrons would seriously limit the tactical air capability to prosecute the air campaign against NVN. Specifically, the loss of two F–4 squadrons would result in an approximate 16 percent loss to the current CINCPAC Combat Sortie Program for Thailand based aircraft.

4. A preliminary review by the Joint Staff indicates that a number of factors, essential to a thorough and objective analysis of the effectiveness of propeller versus jet aircraft in Laos, may not have been fully considered in the study. Some of there essential factors are listed below and discussed in the appendices.

a. Type mission scheduled (Appendix A).³

b. Bomb damage assessment (Appendix B).⁴

c. Day versus night sortie effectiveness in Laos (Appendix C).⁵

d. Muscle Shoals considerations (Appendix D).⁶

e. Enemy air defenses (Appendix E).⁷

5. The conclusions drawn in the referenced study are, in some cases, based on highly questionable assumptions. Two examples are cited: a. since there was no bomb damage assessment made on the majority of over 2,400 night/weather radar controlled level bombing sorties conducted by jet aircraft during the period of the study, the study assumes that there was no destruction of the targets attacked; and, b. the study assumes loss ratios will remain the same in the face of increased enemy defenses and the recent rising trend of propeller aircraft losses in Laos.

6. In summary, the study is too narrow in scope to form the firm basis for a decision to exchange two A–1 squadrons for two F–4 squadrons in Thailand. A more comprehensive study of propeller versus jet aircraft in the overall context of Southeast Asia operations is underway. It is therefore requested that the suspense date for the submission of recommendations on this matter be extended to 1 March 1968 in order to include the results of this analysis.⁸ However, if a decision is required earlier than 1 March 1968, my recommendation, based upon the evidence at hand, would be against the proposed exchange of A–1s for F–4s.

Earle G. Wheeler

1. Source: Washington National Records Center, RG 330, OSD/Admin Files: FRC 73 A 1250, Laos 385.1, 1968. Top Secret. A note on the source text indicates that McNamara saw the “brief.”
2. Document 323.
3. In Appendix A, the Joint Staff stated that one of the “key factors” was consideration of primary mission for which the study gave no consideration. Over 75 percent of the sorties of propeller driven aircraft were armed reconnaissance, while only 33 percent of the jet sorties comprised that type of mission. Armed reconnaissance presented the best opportunities for truck destruction. The jet sorties were targeted 67 percent of the time against interdiction points, structures, truck parts, assembly centers, and other targets that rarely produced confirmed truck kills. The Joint Staff argued that the figure of 9 times more effective was wrong and should be 3.5 times if only armed reconnaissance missions were compared. In a period of good weather, the figure dropped to less than 2 times as effective.
4. In Appendix B, the Joint Staff stated that 93 percent of weather/night level radar controlled bombing was performed by jets. Bomb damage assessment (BDA) was seldom accomplished on these missions. In was erroneous to assume that lack of BDA equated to no results.
5. In Appendix C, the Joint Staff stated that jet armed reconnaissance at day forced truck activity to take place at night. Over twice as many propeller sorties were flown at night as jet sorties.
6. In Appendix D, the Joint Staff stated that Muscle Shoals, an infiltration interdiction system to impede enemy personnel and vehicular traffic, would be operational in early 1968 and would improve effectiveness of both jet and propeller aircraft. The North Vietnamese would therefore improve their air defenses and the slower moving propeller aircraft would become more vulnerable.
7. In Appendix E, the Joint Staff stated that as air defenses improved in Laos (2000 percent since 1965), losses of propeller aircraft doubled while those of jets decreased.
8. In a January 25 memorandum to the Joint Chiefs McNamara approved further study to be completed by March 1. McNamara instructed that the object of the analysis should be to “improve the effectiveness of our interdiction campaign in the Laotian Panhandle.” McNamara specifically asked for information on effectiveness of day versus night sorties; the reasons for high jet sorties during the day in view of the high efficiency of night time prop sorties; the differences in jet and prop efficiency based on mission versus characteristics inherent in aircraft design; the impact of enemy air defenses. McNamara also asked for recommendations on increased use of propeller aircraft in Laos. (Washington National Records Center, RG 330, OSD/Admin Files: FRC 73 A 1250, Laos 385.1, 1968)