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OPERATIONAL LEG CLEARANCES WITH THE MAIN INSTRUMENT PANEL

 

PURPOSE

The purpose of these measurements is to determine the longest leg lengths to obtain operational knee and shin clearances with the main instrument panel.

DISCUSSION

Interference with the main instrument panel and switch guards, controls, and other structures extending aft of the instrument panel, are associated almost exclusively with the upper ends of the range for Buttock-Knee Length. However, total leg length also has an effect.  For that reason data should be gathered on a range of values for combined Buttock-Knee Length and Sitting Knee Height ("combined" leg length or "ComboLeg").  If subjects representing the maximum values for these leg dimensions are not available, larger Buttock-Knee Lengths can be simulated by blocking to a maximum of one inch behind the buttocks.  A corresponding maximum of one inch of aft adjustment in the rudder pedal carriage can be used to simulate larger values for ComboLeg.  Caution must be exercised so that these artificial means of simulating larger body dimensions do not exceed the maxima for these dimensions in the population.

Interference with the main instrument panel may be found to occur with the feet on neutral rudder pedals as well as during the extremes of rudder pedal motion.  All of these conditions are examined.


PROCEDURE

The subject, dressed in flight suit and boots, is installed in the seat, the harnesses are snuggly adjusted and the inertia reel locked with the subject firmly back into the seat. 

Data are first gathered at the full-down seat position.  The rudder pedal carriage is adjusted to the most forward position that permits the subject full-forward throw at maximum leg reach - usually with the knee fully extended.  The subject should be able to operate the rudders and brake without squirming either hip forward.  If the pedal carriage is thereby adjusted to its full-forward position, this fact should be noted.

The subject is instructed to engage the rudder pedal bar at neutral rudders with the balls of the feet, rather than with the heel catch.  This gives the subject a small amount of additional reach. 

Measure the distance between the leg (at the knee or shin) and the main instrument panel, and/or protruding controls and control guards. Measurements are made on both the active and passive legs with full rudder throw.

Measurements are repeated with the seat at one-inch intervals to full-up. The measurement procedure is illustrated below. 

MEASURING SHIN CLEARANCE WITH THE MAIN INSTRUMENT PANEL.

Click on FIGURE for a proposed data form.  


ANALYSIS AND RESULTS

Generally, there is a direct relationship between increases in Buttock-Knee Length and reduced leg clearance to the main instrument panel.  Sitting Knee Height has been found to have only a minor role in affecting such clearance.

Since Buttock-Knee Length is the body dimension most closely associated with leg clearance, data analysis consists of adding the clearance forward of the knees or shins to the subject's Buttock-Knee Length to obtain the threshold clearance value.  The worst-case rudder pedal position, neutral or full right or left rudder, is reported.  The averages of all such values are calculated.  The maximum Buttock-Knee Length to clear the instrument panel in the T-37B is 29.0 inches.
 

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