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INCREASE
TAKEOFF GROSS WEIGHT USING CFM56-7B26/B2 THRUST RATING AND ALTERNATE
CENTER OF GRAVITY The technical
flight demonstrations were performed using the CFM56-7B26 thrust
rating, which currently is the highest thrust rating certified on
the 737-700. A new thrust bump rating, CFM56-7B26/B2, has been offered
to Druk Air as a new product. The CFM56-7B26/B2 thrust rating will produce
at least 2% more thrust than the CFM56-7B26 rating at the Paro International
Airport elevation. The additional thrust is worth approximately
2,100 lb (953 kg) of additional takeoff gross weight at Paro. Takeoff
gross weight can be increased further by using the optimal airplane
takeoff center of gravity (CG) location instead of the conservative
forward-limit location specified by the standard airplane flight
manual (AFM). The increase is achieved by using the AFM-alternate CG takeoff performance option on the 737-700, which allows the operator
to select one of two specified CG locations. Using CG locations aft of the forward limit decreases
airplane drag and lowers stalling speeds, thereby increasing takeoff
performance. For example, using a 23%MAC CG location instead of
the forward-limit location for runway 15 increases 737-700 takeoff
gross weight by 1,200 lb (544 kg). Airport conditions and terrain constraints limited the demonstration takeoff gross weight to approximately 115,000 lb (52,163 kg). However, by optimizing the turn procedures and using the CFM56-7B26/B2 thrust rating and alternate CG performance, takeoff gross weights in excess of approximately 120,000 lb (54,431 kg) are achievable. This improvement would allow Druk Air to fly a 737-700 with a full passenger payload from Paro to all its current initial destinations. |
