The Woracle

Brownout has caused numerous military helicopter crashes in Iraq and Honeywell's synthetic vision technology, which is revolutionising business-jet cockpits, has been picked as part of a solution to the problem. Brownout occurs when a landing helicopter is enveloped in the dust blown up by its rotor. No longer able to see the ground, the crew becomes disoriented.

A cockpit display showing a synthetic view of the landing zone generated from an onboard terrain database, augmented with real-time information on obstacles detected by a millimetre-wave radar that can see through the dust, is part of the brownout solution being developed by the US Defense Advanced Research Projects Agency under its Sandblaster programme.

The intent is to have a system ready for operational use within 18 months. That will be none too soon.

With the V-22 Osprey scheduled to begin its first operational deployment to Iraq in September, I asked the Sandblaster folks at DARPA whether the tiltrotor, with its rotors perched at the tips of the wing, was any less prone to brownout than a conventional helicopter. On the contrary, based on tests done for DARPA, it's worse. "Never seen a dust cloud like it," they said. "The crew said they had to throw away their flight suits after - and they didn't specify why!"

China-watching website sinodefence.com has posted perhaps the clearest picture yet of China's Z-10 attack helicopter. The site says the Z-10 first flew in 2003 and is expected to enter service in 2008-9.

Changhe Z-10 (sinodefence.com photos)

The Changhe-built Z-10 looks to be in the same class as the Agusta A129, Denel Rooivalk and Eurocopter Tiger. It has a five-blade main rotor and X-shaped tailrotor; targeting and pilotage sensors on the nose and gun underneath; sloped fuselage sides and stub wings carrying four Hellfire-class HJ-10 anti-tank missiles per side.

The Z-10 is powered by a pair of Pratt & Whitney Canada PT6C-67Cs, says sinodefence.com, but the bulged nacelle looks a little different on this aircraft. There is no side-facing exhaust as seen in other pictures on the site (right). Whether that white "chute" is an exhaust suppressor - or even part of the helicopter - I can't tell.

The Z-10 looks competent enough, but a lot depends on the quality of the sensors, weapons and communications networks - things you can't tell by looking a picture.

The US Defense Science Board has just released its report on the VSTOL/STOL airlift requirements to support the US Army's concept of "mounted aerial manoeuvre" - flying a fully equipped armoured force from an intermediate land or sea base directly to the battlefield.

The report is important to two camps: the US Army backing the Joint Heavy Lift rotorcraft (left) and the US Air Force backing the AMC-X (right, aka AJACS) replacement for the C-130.

(Artwork via www.secretprojects.co.uk)

Both camps are eyeing the Army's requirement to airlift payloads of up to 30t over distances of 250-500nm, using either fixed- or rotary-wing aircraft. And the report has good news and bad news for both.

Steve Trimble over on The DEW Line reveals Boeing has a DARPA contract to study a disk rotor high-speed rotorcraft. Like most things in aerospace these days, this is not a new idea.

Swiss architect and designer George Vranek, on his diskrotor website, traces the concept of a circular rotor with retractable blades back to Germany in 1962 and also mentions a 1992 NASA Ames study.

US engineering firm owner Frank Black has tried for years to find backers for his Modus Verticraft concept, and now Nowegian firm SiMiCon is working on a retractable-blade disk rotor UAV.

Perseverance pays off, and Piasecki Aircraft appears to be having some success with its X-49A "Speedhawk" - a Sikorsky H-60 modified with Piasecki's vectored-thrust ducted propeller (VTDP). The attached video shows the helicopter has exceeded 170kt in flight testing.

The X-49A is flying at Boeing's test centre in Delaware, and Dave Harvey on rotorhub.com, says the US giant is interested in combining the VTDP with the optimum-speed rotor technology from its A160T Hummingbird unmanned helicopter. That would make an interesting combination.

The Salt Lake Tribune has just run a profile of local gyroplane developer Groen Brothers Aviation. It contains a brief reference to "design issues" uncovered in September during the preliminary design review for the Heliplane high-speed rotorcraft demonstrator GBA is designing for DARPA.

So I contacted DARPA, which said: "We underestimated the difficulty in achieving 400mph cruise performance with an existing engine and airframe. Nobody has ever flown a rotorcraft at 400mph." Understatement - the fastest a rotor has flown sideways is 249.1mph, attached to a Westland Lynx in 1986.

GBA calls the Heliplane a "gyrodyne": it takes off and lands like a helicopter using a tipjet-driven rotor, but cruises like an autogyro, with the rotor unpowered and thrust provided by a pair of turbofans. Gyrodynes are not new, but pushing one to 400mph is - that's twice the speed McDonnell's XV-1 Convertiplane tipjet compound autogyro achieved in 1956.

Designing a reaction-drive rotor system that can produce sufficient lift, generate minimum drag, carry the loads and be stable at high speed has proved to be a challenge. DARPA says GBA is working to resolve "a few remaining design issues", then it will decide whether to proceed to full-scale windtunnel testing of the rotor system.

On the subject of compound autogyros, Flight International alumnus Stewart Penney points me to this great video of the Fairey Rotodyne - Groen's inspiration for the Heliplane gyrodyne. The Rotodyne's rotor was tipjet-driven for take-off and landing and autorotated in the cruise, propulsion being provided by a pair of Napier Eland turboprops. The Rotodyne set a speed record of 190.9mph in 1959, but was cancelled in 1962 for reasons more political than technical.

Popular Science has included the Bell Boeing V-22 Osprey in its "The Best of What's New" list for 2007. Not bad for an aircraft that entered development 25 years ago. Makes up for Time magazine's shoddy "special investigation" into the V-22, and gives me an excuse to run this great picture of a US Air Force Special Operations CV-22, somewhere in New Mexico.

(USAF photo)

In case you wondered, other winners in PopSci's "best of 2007" aviation & space category include Cessna's Flycatcher, sorry Skycatcher light sport aircraft, Boeing's EA-18G Growler "jammer jet", and Eclipse's Concept Jet (maybe they will build it now).

The US Marine Corps has just released this rare image of an MV-22 Osprey tiltrotor operating in Iraq - there are green rotor-tip lights, the Marines now tell me. (US Navy photo)

Working on a Chinook feature, and I found this...

"Shall we dance?" (RAF Chinooks - Crown Copyright)