– 5 –
on which a dual sprocket assembly is mounted. The sprockets are connected to the common drive shaft by shear rivets, and each transmits rotation of the drive unit through roller chains to an irreversible jackscrew. Failure of either set of shear rivets freezes the stabilizer in the last selected position, and further operation is impossible. The indication of stabilizer position is provided by fore and aft movement of a small "bug" along a scale on the left side of the center console.
Longitudinal control of the aircraft may also be accomplished through the autopilot which utilizes elevator displacement to initially retain the selected attitude. An automatic trim coupler senses elevator servo torque information and generates stabilizer trim commands when torque of a given value or time interval is encountered. Any "runaway" or contradiction in the system results in the interruption of power to the autopilot and the illumination of a warning tight
Attitude information in N8607 was provided by a Collins 105 Approach Horizon through movement of the "miniature airplane" in reference to the all-black face of the instrument. It has no indices for the degree of pitch, and the displayed rate of pitch change varies as follows
| Attitude Range | Display Ratio |
|---|---|
| 00-20 degrees | 0.033 inch/degree change |
| 20-70 degrees | 0.012 inch/degree change |
| 70-85 degrees | 0.006 inch/degree change |
Thus it is possible for the instrument to indicate a reduced rate of pitch when attitude changes through 20 degrees of pitch, even though the actual rate of change is constant. In a corresponding manner if the attitude has exceeded 20 degrees, the displayed rate of aircraft response to control inputs wall be slower than the actual response.
There were five discrepancies on the continuous maintenance log: (1) Fuel totalizer reading wrong, (2) Outer pane center windshield heat inoperative, (3) No. 3 engine ejector light blinks, (4) No 3 main fuel gauge reads 2-4,000 pounds high, and (5) PTC inoperative.
1.7 Meteorological information
The U. S. Weather Bureau (USWB) aviation area forecast, valid 0100-1300, indicated a surface wave off the Louisiana coast was expected to move eastward at 30-35 knots, with ceilings at 400-800 feet and moderate to occasionally heavy rain. A north-south line of showers and embedded thunderstorms north of the wave crest was expected to produce moderate to severe turbulence in the thunderstorms and heavier showers, and moderate or greater clear air turbulence was forecast from 24,000 to 40,000 feet, throughout the area. The EAL system forecast, valid 0000-1200, predicted ceilings below 1,000 feet, light rain in the Pensacola-New Orleans area, improving to 1,200-2,500 feet as the low center moved eastward. Turbulence[1]
- ↑ EAL utilizes a numerical scale to delineate the severity of turbulence within a given classification, 1.e , 4-6 is moderate, 7-9 is severe, and 10 is extreme.
