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The speed brake (spoiler) lever in the cockpit was found in the full forward position. Movement of this lever did not produce any cable movement aft of station 41. Investigation disclosed that this was due to the cables being restricted by crushed metal in the area and being slack of the restriction as a result of upward crushing of the lower fuselage structure in the nose wheel area. Examination of the Speed brake (spoiler) system, including operational functional tests on com- ponents, failed to reveal any evidence that would have precluded normal operation prior to water impact. The landing gears were down and locked, and the flaps were fully extended (50°) at time of impact with the water. The Nos. 1, 3, and 4 engines separated from the aircraft at water impact. Examination of the aircraft struc— ture, powerplants, and flight control systems revealed no ev1dence of failure or malfunction prior to impact with the water.
The aircraft brake system, including the anti-skid dev1ce, was examined and functional tests were conducted on the components. This examination disclosed no evidence that would have precluded normal brake operation prior to impact with, and submersion in, the salt water of Thurston Basin.
Measurement of the remaining tread depth on each of the MLG tires revealed the following:
| Left MLG | Right MLG | |||
| No. 1 | No. 2 | No. 3 | No. 4 | |
| Front tires | .100" | .234" | .218" | .109" |
| Rear tires | .234" | .281" | .072" | .062" |
The following has been extracted from test data submitted by the Boeing Company in response to a request by the Civil Aeronautics Board.
Wet Runway Stopping Distance
Model 707-139 With JT30—6 engines
50° flaps with gear down
Zero wind and zero runway slope
Sea level, standard day
| Gross Wt. | Brakes (Anti—skid on) | Max. Rev Thurst | Spoilers 60 degrees fully extended) | Stopping distance from touchdown | |
| Smooth tires | New ribbed | ||||
| 196,000 lbs. | Yes | Yes | Yes | 4,150 ft. | 2,750 ft. |
| 196,000 lbs. | Yes | Yes | No | 4,350 ft. | 3,050 ft. |
| 190,000 lbs. | Yes | Yes | Yes | 4,000 ft. | 2,650 ft. |
| 190,000 lbs. | Yes | Yes | No | 4,250 ft. | 2,950 ft. |
These distances were calculated utilizing approach and touchdown speeds of 146.6 and 142.2 knots IAS respectively, for a gross weight of 196,000 pounds and 144.3 and 140.0 knots IAS for 190,000 pounds. The following assumptions were also used in the calculations.
