#5 Cruising Flight
To assess your ability to establish the aircraft in cruising flight in accordance with the POH.
You will be requested to establish cruise flight at a power setting specified by the Examiner in accordance with the performance charts in the POH, placards displayed in the aircraft, or any other means authorized by the manufacturer.
Acceptable performance will be based on the following:
- Achieve the specified cruise power setting by setting the throttles, propellers and mixture controls for existing conditions as recommended in the POH;
- Apply any additional measures recommended by the manufacturer with respect to aircraft configuration or other considerations.
This exercise—which is based on knowledge of the cruise data in the POH—is not included in the practical flight training that precedes the flight test, but it will be assessed in the oral examination that precedes the flight test.1 Therefore, you must ensure that you have an operational knowledge of the cruise performance requirements for the Seneca—specifically, be sure you understand the use and application of the Cruise Performance—Range Graph that appears on p. 9-10 of the POH.
For setting the mixtures during cruise flight, you would, of course, use the EGT2 gauges to fine-tune the flow (applying the 100°F rule).3 The operational rules for Langley Flying School’s Seneca, however, prescribe that the mixtures cannot be leaned during flight at or below 5000’ ASL. If fuel leaning is required at higher altitudes, the mixture levers are only pulled back until a very slight temperature increase is notice—i.e., the EGT needles come off the stops and begin to register a temperature change.
1 Technically, the Examiner could require during flight that you establish the aircraft in cruise as per a prescribed power setting determined from the POH, but this would be unprecedented in flight tests. Normally, candidate knowledge of this is determined by oral questions in the pre-flight portion.
2 Exhaust Gas Temperature gauges.
3 The 100°F rule for working the EGT gauge is as follows—lean mixture to peak EGT, then enrich by 100°F (cooler from peak) for best power mixture. Enriching by only 25°F will give you best economy mixture, but this higher operating temperature is not very economical for engine longevity—too hot for the cylinders. Normally the red-line or red-needle markers are set to the aircraft’s peak EGT position.