Posted on

Supersonic noise suppression could allow US flights

Research into minimizing the sonic boom that occurs as an aircraft flies at Mach 1 and beyond is continuing at NASA and commercial aircraft makers.  Efforts to modify the N-wave, the shock wave which occurs at speeds in excess of Mach 1,  have been ongoing at Gulfstream, in conjunction with NASA. Using a modified F-15B fitted with a telescoping boom flight tests have been promising creating a smaller n-wave which will  greatly reduce the noise heard on the ground from “sharp crack to a quiet whisper”  according to a presentation which Gulfstream gave to the FAA sponsored Advanced Technologies and Supersonics  symposium in 2009.  The boom, which can extend to 24 feet from its 14 foot-long  retracted position, is constructed using composite materials. According to Gulstream, the Quiet Spike, results ” in a softer sound that is 10,000 times quieter than the Concorde.”

In 2005, Lockheed patented “Passive aerodynamic sonic boom suppression for supersonic aircraft” which also addresses the area of the aircraft’s nose as a way to mitigate the pressure wave propagating from the airframe. A gull wing, as well as modified body form created by pinching the fuselage at the mid-point also is identified to reduce noise.

In 2008, the FAA issued a statement indicating that it would be open to new rules allowing for the operation of supersonic aircraft while over land. This change, would allow supersonic operation of aircraft meeting Stage 4 sub-sonic noise requirements. Currently, supersonic aircraft which meet this noise threshold cannot operate in the US.

Posted on

Future fast helicopter to push 250 knots advances

Sikorsky helicopter is testing its X2 demonstrator in hopes of combining the flexibility and hover of helicopters with the speed and range of airplanes. Flight tests continued with the first engagement of the rear pusher propeller which, in theory, should enable the hybrid to speeds of 250 knots. The helicopter generates lift with two counter rotating main rotor blades, in addition to the rear pusher. This arrangement makes torque more manageable and needs only to be addressed for the pusher rotor.

Sikorsky’s challenge in attempting a 250 knot helicopter was to counter the loss of lift of the retreating main rotor blades as the airframe travels forward.  This is being addressed by using a rigid rotor which uses the Advancing Blade Concept (ABC) with which the retreating blade produces little or no lift.  First pioneered with the Sikorsky XH-59A, a turbojet powered experimental helicopter, the ABC allowed it to reach 240 knots in 1973.  Then current technologies made it impractical, though.  More advanced “fly by wire” flight control systems have allowed greatly improved handling characteristics in the X2 demonstrator.

Sikorsky XH-59A

Sikorsky XH-59A

Recently, Sikorsky announced the X2 TECHNOLOGYTM Light Tactical Helicopter (LTH) in anticipation of flight tests confirming the capabilities of its demonstrator.  It is envisioned to compete with other smaller combat helicopters like the Eurocopter AS 550 Fennec and HAL Light Combat Helicopter (LCH).

“These technologies can potentially bring new rotorcraft capabilities that, to date, have been unachievable by the industry,” said Sikorsky President Jeffrey P. Pino. “In addition to doubling the speed of helicopters, this technology can improve hot/high performance, maneuverability and low acoustic signature. Sikorsky’s Light Tactical Helicopter concept demonstrates a way to package these capabilities into an airframe that is tailored to meet a range of military missions.”

Posted on

How EFIS may be killing pilots

EFIS Primary Flight Display

EFIS Primary Flight Display

Something has been gnawing at me in aviation, which may spell trouble for relatively low time commercial pilots.  Chances are today aviators who  are training to become a professional pilots are doing so in one of the current generation of trainers.  This means that they are probably using a modern EFIS equipped Cessna G-1000 or Cirrus Avidyne aircraft as a primary trainer.  Continuing on toward the Instrument rating, pilots are fully integrated and comfortable with utilizing all of the capabilities of these truly remarkable pieces of avionics.

"Six Pack" Analog Instruments

“Six Pack” Analog Instruments

Trouble is, that while today’s pilots are trained in these thoroughly modern avionics suites,  they are then thrust into the world of down and dirty entry level freight and Part 135 position flying old Cessna and Piper light twins.  These aircraft, while capable, are equipped with  the pre-1960’s technology of the “six pack” and analog instrumentation.

It is probably safe to say that by almost all accounts, the transition from analog instrumentation to modern EFIS equipped cockpits is not difficult, the same cannot be said the other way around.  Scans must be developed and perfected in a way that takes much longer to achieve.  This is due to the way the information is presented and the physical distance that the eye much travel.  For a low time pilot who is in their first 100 hours or so, it could spell trouble.

EFIS was designed specifically to rectify the flaws that occur in flying with the previous generation of analog instrumentation. Studies of the scanning of the primary and secondary instruments  were carefully researched and used to design the Primary Flight Display (PFD) which is now standard in all airliners and now being incorporated into more and more GA aircraft.

I hope that this will be identified as a hazard and that additional training may be incorporated prior to these pilots flying the line.