Technical analysis of hijacker's possible landing envelope and search priorities
This copy: Part 110 pp. 267–268Also filed at Part 18 pp. 414–415 (primary) · Part 60 pp. 312–313 · Part 93 pp. 40–41 · Part 93 pp. 46–47
This copy’s own title
Analysis of envelope of possible hijacker landing points using radar and flight data
Document date 9 January 1972
Another copy of this document is the primary, most legible copy: Part 18 pp. 414–415.
Copies may differ in what was redacted.
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Id: Cooper-Part-110:267-268
Subject: Cooper Files: Cooper-Part-110:267-268 Document: Analysis of envelope of possible hijacker landing points using radar and flight data Id: Cooper-Part-110:267-268 Page: https://cooper.theunsolved.net/documents/Cooper-Part-110%3A267-268 What is wrong (title, date, type, which pages belong together, copies)? What does the scan show?
A person reads every report. Corrections are made by hand, to the data — titles, dates, names, which pages belong together — never to the scans, and they can take a while to appear.
FBI 164-81, Vault Part 110 pp. 267–268 (DB Cooper-566–567), Report, dated 9 Jan 1972 — cooper.theunsolved.net/documents/Cooper-Part-110%3A267-268
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The attached plot indicates the envelope of possible landing points of the high jacker (HJ). It is based on the following:
— Aircraft position from USAF radar data from McChord AFB furnished by [REDACTED]
— Probable jump time (0411 GMT) from an analysis of the recorded communication from the flight relative to the cabin pressure fluctuation. Flight tests conducted on January 6 confirmed that the pressure fluctuation almost certainly occurred at the time the HJ left the airplane.
— Wind information from 10,000' MSL to the ground as determined by [REDACTED]
— Human body trajectories from data furnished by The Boeing Company (free-fall) and [REDACTED] who is an expert para— chutist.
— Time correlation from the above USAF radar information and from the NWA communications network tape recording.
— Airplane airspeed and altitude from the airplane's flight recorder.
The plot is explained as follows:
1. The heavy dashed line C—D—E—S defines the airplane's probable ground track.
2. Line G—I—J—K defines the westernmost, and Line L—M—N—O the easternmost probable airplane ground tracks based on the stated position tolerance of ±.5 nautical mile of the USAF radar plot.
3. Lines A—B, H—P, and O—R are the average wind vectors between 10,000' MSL and the ground, and are the lines parallel to which the HJ would drift after the parachute had opened.
4. Line H—S—T defines the northernmost (earliest) points over which the HJ probably left the airplane. Line K—F—O defines the southernmost (latest) points over which the HJ probably left the airplane. The north—south span of possible jump positions is a product of the radar position tolerance of ±.5 mile, and the possible communication time determination tolerance of ±1 minute.
5. The area within the boundary defined by Points H—P—Q—R—O—K—J—I—H marks the extreme limits of probable landing points based on the above tolerances. That is, assuming the highest probable degree of inaccuracy in aircraft position, jump time, wind vector, etc., all probable HJ landing points would lie within the area defined by this line.
6. If it is assumed aircraft position, jump time, wind vector, and other inputs used are all accurate (without allowance for the above stated tolerances):
a. The HJ's landing point would be at Point A if his 'chute did not open, or if he opened it so soon that the high speed caused 'chute damage that resulted in the equivalent of a free—fall to the ground. (The horizontal body trajectory due to
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DB Cooper-566
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it being at the same speed as the airplane at the moment of exit, has been ignored since it would be a maximum of 2600' along the airplane's track if the HJ free-- fell all the way to the ground in the "least drag" (tucked) position.)
b. If the 'chute was opened without damage immediately after the HJ left the airplane, he would drift with the wind along Line A--B and would land at Point B. The more expert he was, the longer he would probably free--fall (to limit his drift with the wind). The lowest probable altitude to which he would free--fall is 2500' MSL. If he free-- fell to 2500' MSL, his landing would be at Point U.
Based on the above, the most favorable search areas, listed in their order of priority, would be as follows:
-- At Point A.
-- Along Line A--B, favoring the segment between U and B.
-- South of Line A--B.
-- North of Line A--B.
In addition to the above, the following are pertinent:
-- The landing point is more likely to be south of Line A--B, and it is more likely to be in the northwest portion of area A--B--R--O--K--J--A than in the southeast portion thereof.
-- It is substantially less likely that the landing point is north of Line A--B. If it is, the most probable point is south of the Lewis River, and in the southwest portion of the area defined by Points A--B--I--J--A.
-- It seems highly unlikely--though possible--that the landing point is north of the Lewis River, but if it is, it is more likely to be in the southwest portion of the area defined by Points Q--M--V--I--H--P--Q.
If there are any questions relative to the above, they should be referred to the under-- signed.
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[redacted signature block] Northwest Airlines
January 9, 1972
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