The US Federal Aviation Administration has awarded a supplemental type certificate (STC) to DuganAir Technologies for a modification package which allows Boeing 727-100 and -200s to meet Stage 3 requirements without hushkits.
The "Quiet Wing System" has been under development for four years. It combines winglet technology developed by Winglet Systems with modifications developed by DuganAir in one package. "We took their STC, combined it with our own, removed the centre engine thrust reverser and added an acoustic tube in the inlet," says executive vice-president of operations, Ronald Mcintosh.
DuganAir says the package increases the performance of the aircraft, allowing an increase in gross weight to 95,300kg, or up to 5% payload growth, with the same fuel. "In some cases, it will extend range by as much as 13% because of the winglet design," adds Mcintosh. The company also claims that the cost of the -200 conversion is roughly half that offered by competing hushkit packages. Costs are in the $1.3-$2 million range per aircraft, depending on weight, compared with $1.8-$3 million per engine hushkit. Modification time is also down to around seven working days.
Orders have been received for 32 conversions to date, 10 of which are for -100s. Of the -200s on order, four are passenger versions, says DuganAir. Canadian company Kelowna Flightcraft has ordered seven kits for its 727 freighters, while US carriers Sun Pacific International and Express One International have contracts for two and nine kits respectively. Unannounced deals account for the remainder of the orders.
Kelowna is performing the initial conversions in a partnership with DuganAir, called Quiet Wing Systems. The bulk of the work will eventually be extended south to three unidentified modification centres in the USA, with sites located strategically on the West and East coasts and in the Midwest, says Mcintosh.
In addition to the noise treatment of the inlet, the package contains a flap and aileron droop system. This produces more lift at lower speed, allowing the aircraft to climb and land at reduced power settings. The removal of the third engine thrust reverser decreases aft centre of gravity by almost 1,100kg, reducing overall weight and enhancing balance.
Source: Flight International
