John Croft: March 2009 Archives

A picture from the Broward County Aviation Department in Florida shows the outcome of a collision between a Cessna 402 and a 20lb turkey vulture after the aircraft departed the Fort Lauderdale-Hollywood International Airport last month.

According to the Miami Herald's account of the incident, the pilot had climbed to an altitude of about 600ft when the two met. The pilot fared better in the end, with injuries to the head and face but a successful emergency landing back at the airport under his belt.

A chilling account of a similar event, also in Florida and also with a turkey vulture, is described on the Aircraft Owners and Pilots Association website...

Pratt & Whitney's geared turbofan, the engine of choice for Mitsubishi's regional jet and Bombardier's new C-series jets, will break sound and fuel consumption barriers, but it could also help with the ever-growing threat from Canada geese.

The 7-20lb birds were the culprits in the downing of US Airways Flight 1549 in the Hudson River in early January. A crack cabin crew and good fortune kept all 150 passengers and crew relatively healthy that day.

Engine manufacturers, when certificating their products, must prove that a jet engine can withstand an impact with an 8lb bird, but in this case "withstand" doesn't mean "perform". The regs state the engine can't catch fire, can't burst, can't rip from the aircraft and must be capable of shutting off.

Below is a video showing the 8lb bird strike test on a Pratt & Whitney PW4098 turbofan, an engine available for the Boeing 777. Post-impact damage shows the permanent deformation of the hollow titanium fan blades.

For smaller birds weighing 2.5lb, the engine must continue to run at 75% power for 20 minutes, enough time to perform a go-around (assuming the bird hit occurred on arrival) and successful return to the airport.

CFM obviously met the 8lb challenge. Though not producing enough thrust to keep the aircraft aloft, both of the Hudson Airbus A320's two CFM56 engines held to their certification requirements.

However Pratt & Whitney's PW1000G geared turbofan (GTF), a possible choice for a new generation of airliners that will eventually replace the A320 and Boeing 737 in the 2020 realm, should be more resilient to such encounters.

Pratt & Whitney chief engineer Paul Adams explains that the bird threat at relatively low altitudes comes not primarily from the forward collision speed of the bird with the engine, but from the high velocity impact of the spinning fan blade chopping into the bird.

If a 112-inch diameter fan is spinning at 3,000 rpm at full power, each blade at the tip (about 4ft from the hub) will be traveling at a speed of about 850 mph. In the Hudson River case, the forward speed of the bird-engine collision would have been about 200 mph.

With GTF technology, the fan blade spins about 30% slower than for a typical turbofan engine however, owing to a gear reduction system that separates the fan from the low pressure turbine (LPT) portion of the engine. Typically the high-pressure turbine powers the high pressure compressor while the LPT powers the low pressure compressor and the fan. For modern high bypass engines, the fan blade provides about 80% of the engine's thrust. 

Adams says the reduction in speed means the kinetic energy of the collision will be about 50% less than with conventional turbofan engines, potentially giving the engine a higher probability of surviving encounters with birds and geese.

The video below, created by Pratt & Whitney, shows how the gear reduction system works.

4/2/2009 - VIDEO removed at the request of Pratt & Whitney due to proprietary content...

Move it on over, Terrafugia; Step aside, Sampson SkyBike...

Boeing has applied for a US patent (#20090081043) for its own "roadable" aircraft, or flying car. Its an autogyro with a scissor-type, deployable main rotor (that looks to be asymmetrical) that the company says is better than competing storable and transportable designs in which the rotors fold at the hub or telescope out.

Anyone have a clue as to what Boeing might be thinking?

Northrop Grumman today (24 March) received approval for a US patent for an "ornamental design" for a flying wing aircraft with canard.

Bill Sweetman, on Av Week's Ares blog, sheds some light on a similar patent for the aircraft, sans canard.

Honeywell Aerospace has completed its work with Sikorsky and Sierra Nevada Corp as part of the Defence Advanced Research Projects Agency's (DARPA) "Sandblaster Program", and in the process has provided a glimpse of the future of computer and sensor-aided vision, systems that will help pilots safely takeoff and land in any environment, hence the so-called "electronic bumper."

Above on the left is the picture from recent Sandblaster tests in California showing actual conditions in front of the helicopter, and on the right, a synthetic recreation of the forward environment (photo is courtesy of Sikorksy) that pilots used to guide their helicopter to landing. Though the truck looks more like terrain than vehicle to the radar, both are to be avoided on landing.

At the heart of Sandblaster is Honeywell's inertial database, populated with terrain and obstacle data (part of Honeywell's terrain awareness and synthetic vision systems) and fused with 94GHz millimetre wave radar data collected by a Sierra Nevada radar imaging a 30x30-degree field of view at 2Hz update rate.

The package flew on a high tech version of the Sikorsky UH-60 Black Hawk ( View image) modified by NASA and the US Army for fly-by-wire capabilities and other upgrades. Sierra Nevada's radar ( View image) was located under the nose of the helicopter.

During three days and 32h of testing from 12-14 January, three Army pilots with no previous flight time on the "Sandblaster" system were able to position their helicopters close to a landing on a variety of terrain types and slopes with no external visual references, which was the basic gist of DARPA's now-completed project....

A proposed "order" from Federal Aviation Administration set to run in tomorrow's (19 March) Federal Register got me running for my American Heritage College dictionary.

There in the 10-page report was a word that I don't think I've ever seen in the context of aerospace journalism.

The order itself has to do with the FAA wanting to keep aircraft bird strike data to itself, and might make it virtually impossible for you, the public, to use the Freedom of Information Act to get at raw wildlife strike data from airlines, pilots and airports in the agency's accumulation of 19 years of incident data.

What's the big deal you ask?

"The agency is concerned that there is a serious potential that information related to bird strikes will not be submitted because of fear that disclosure of raw data could unfairly cast unfounded aspersions on the submitter," officials write.

What happens to one who has been the victim of the "aspersions" that have been cast, you ask?

Based on AHD definition #2, I'd like to think they might go to heaven....

Terrafugia has revealed that its Transition roadable aircraft achieved first flight on 5 March. The company is holding a press conference at 9:30 am in Boston this morning to discuss. Meanwhile they've posted three videos on their website...

Video 1 - First camera angle

Video 2 - Alternate camera angle

Video 3 - Interview with test pilot

Several late breaking updates to Sunday's Cirrus save

• I'm told there were no problems with the engine in Sunday's accident. While there may have been a mechanical distraction, spatial disorientation in instrument conditions was more likely the main factor that put the aircraft into an attitude from which the pilot felt that pulling the parachute was the only means of recovery after trying to return to the airport and breaking out below the cloud deck.

• If the pilot lost situational awareness in the clouds, it could be that he also became concerned about his position in relation to the Washington DC area "no-fly" zone around the city centre, a ring of airspace that extends outward toward the Montgomery County Airpark, where the pilot departed. General aviation pilots and aircraft entering that zone without becoming certified (with fingerprinting and background check) and having a special clearance are intercepted by patrolling aircraft, and possibly shot down if they don't comply with instructions. That kind of pressure certainly doesn't help one get his act together in a stressful situation, in fact it may have proved deadly in a crash that killed two at a nearby airport in January 2008. Here's the report

• Cirrus officially lists 17 chute activations, including Sunday's, and 34 "saves". Officials have not yet included statements from eyewitnesses to a SR20 crash in Florida that could raise the total activations to 18, but not increase the saves. An except from the report reads: "Two witnesses in the same neighborhood stated they were checking their mail between 1430 and 1500, when they heard an airplane flying overhead. They observed the airplane flying eastbound between 225 to 250 feet above the trees. Both witnesses stated, "the engine was heard to quit and the airplane made a sharp turn to the right." The nose of the airplane pitched down vertically and the airplane started spinning. Just before the airplane disappeared below the tree line, the witnesses observed an orange or red parachute deploy, but the parachute did not inflate."

The pilot of a Cirrus SR22 who departed the Montgomery County Airpark (GAI) in Maryland Sunday afternoon can count himself among the 30 people "saved" by the aircraft's rocket-powered parachute system, according to my count. A photo from FlightAware.com clearly shows 55ft chute in the aftermath of Sunday's deployment.

I see from the Cirrus owners and pilots association (COPA) that as of the end of 2008, there had been 16 known Cirrus airframe parachute system (CAPS) activations which saved 29 people.

There are have been at least two this year, including Sunday's. Pilots in an SR22 that crashed in Florida on 17 February had pulled the chute, but the aircraft was low to the ground and spinning vertically at the time, according to an eyewitness. Both were killed.

In at least two cases, deployments failed due to speed or faults. 

"The two deployment failures involved one activation at very high speed (likely twice the deployment speed), and the other activation where the rocket took an unusual trajectory resulting in a failure to open the canopy. The trajectory anomaly resulted in an airworthiness directive for modifying the CAPS rocket assembly," COPA says. Graphic below is from COPA website.

COPA COPA notes that descents under the fully formed canopy happen at 1,700 feet per minute, which equates to a vertical velocity of 28 feet per second or 17kt, enough to break the aircraft but save the people. 

During certification Cirrus demonstrated a chute deployment at 133kt. In practice however, pilots have pulled the red handle in the aircraft's headliner....

... and successfully deployed at much higher speeds, perhaps as high as 190kt. In another case where the aircraft was traveling at speeds estimated to be more than 240 knots, the parachute did not successfully deploy, says COPA.

At GAI, the pilot had just departed on an IFR cross country flight when he encountered mechanical problems, most likely of the engine variety, and could not maintain altitude back to the airport. His speed was probably just right for popping the chute though.

I just received an invitation from Terrafugia, a company run by some very smart ex-MIT types who are developing a "roadable aircraft".

Yep. A flying car.

Not just a paper project, but a vehicle just as real as Molt Taylor's AeroCar from the 1950s.

As of Christmas, Terrafugia CEO Carl Dietrich had said the composite Transition was in the final preparations for high speed taxi tests and perhaps, just maybe, first flight.

I hadn't heard anything more until I got this invite in the email just now...

If I were a betting man, I'd say FIRST FLIGHT has been completed, and that everyone walked away smiling.

Here are some additional details on the vehicle.

• $194,000 price tag
• Powered by a 100hp Rotax 912S four-stroke engine
• 100kt cruise speed and 400nm range (air)

A video Terrafugia posted on YouTube shows how the Transition transitions.

Ford Motor company has put up one if its prize possessions for sale, by all accounts a victim of the public relations nightmare set off when chief executives of the Big 3 US automobile makers flew their business jets to Washington last year to ask Congress for money to keep their businesses operating.

While those of us in the aviation industry know why taking the private jet to DC makes sense (security, value of time, efficiency, connectivity, etc etc), this practicality often conflicts with the romantic notions of the general public about business jets -- corporate fat cats having Roman orgies in their aerial chariots with gold trimming.

Though some of these aircraft are indeed chariots, see for yourself if Ford's Fokker F28** on sale now at Airliners.net, fits the bill....

The sellers don't think so either.

Their sentiments at the bottom of the ad are Ford Tough as well:

"Corporate aviation witch-hunters take note....there are no staterooms, showers, hot tubs, or gold-plated shuffleboard courts visible anywhere in the cabin. Simply 48 business-class seats, perfect for transporting a number of employees from one location to another without paying them to wait in security lines, sit in the airport during delays, or deal with lost luggage."

**N324K is colloquially known as the Fokker 70, a newer version of the F28 developed in the 1990s. Officially, per its registration, the aircraft is an F.28 MK 0070.** 

It's no secret that the emergency air medical services industry is a quandary as Congress and regulators ponder its abysmal accident record with an eye on more regulation.

Officials with the Association of Air Medical Services (AAMS), the industry's main trade group, didn't score any points with the regulation gods in an email to reporters as part of the lead-up to their meetings in Washington DC this week however. (Though they did provide a bit of comic relief to this blogger)

See if you can spot the blunder in the title for the FAA's John McGraw at Wednesday's meeting:

Wyoming, Delaware, that is...

Gulfstream yesterday announced further cuts in its 2009 delivery projections, this time to the popular large-cabin sector as the economy further declines and customers cancel or delay orders.

The slow-down is also forcing the Savannah, Georgia-based manufacturer of business jets to lay off 1,200 employees in several locations, 12% of its workforce.

New targets for large-cabin jets stand at 73 "green" aircraft deliveries for 2009, down from the 94 announced in January. The January large-cabin guidance, which in hindsight appears overly optimistic, represented a 7% increase in the segment, up from 87 large-cabin deliveries last year.

The company in January had said it would slash production of its mid-size jets 50% this year compared to last year, down to 30 from 69.

The velocity-squared element in the kinetic energy equation helps explain recent revelations by Sikorsky that aftermarket cast acrylic windscreens available for its S-76 series twin-engine helicopters require a lower maximum speed compared to the original equipment manufacturer (OEM) alternatives.

Sikorsky issued an "all-operators" note on 17 February addressing windscreens in the aftermath of a fatal Petroleum Helicopters S-76C++ in Louisiana on 4 January. The gist of the letter is that the cast windscreens can handle less impact kinetic energy than the glass or stretched acrylic versions of the component, meaning operators using the cast parts have to fly significantly slower to obtain the same level of protection. That's because energy increases with velocity-squared...

Investigators examining the crash have found traces of a hawk on the pilot's windscreen and other parts of the helicopter, raising the spectre that the collision between the bird and the windscreen at 138kt caused the helicopter's power to decrease (revealed by the flight data recorder) and cabin noise to increase (revealed by the cockpit voice recorder), precipitating the subsequent dive and crash into swampland below.

The kinetic energy (KE) of a 1kg (2.2lb) bird, about the size of a hawk, hitting a helicopter flying at 138kt is 2,520 Joules. That number is not especially significant until you consider the following...

PHI equips its S-76 fleet with an FAA-approved cast acrylic windscreen certified and sold by Aeronautical Accessories, an affiliate of Bell Helicopter.

As delivered by Sikorsky, the S-76 has a laminated glass windscreen built and tested to withstand a 1kg (2.2lb) bird strike at speeds up to the "never exceed" (Vne) speed of 155kt, according to Vaughan Askue, S-76 sales support engineer for Sikorsky.

A 1kg bird hitting a helicopter traveling at 155kt has 3,179 Joules of KE.

The FAA did not require the bird strike test when the S-76 model was first type certificated in 1978, though Sikorsky went ahead and designed and tested to the more stringent 1kg at Vne UK Civil Aviation Authority rules, which the FAA adopted for new build helicopters starting in 2004 (FAR Part 29 Amendment 47).

Sikorsky later developed a stretched acrylic windscreen, also built to handle a 1kg bird at 155kt, that it says has the equivalent protection as glass, but does not require an AC generator to power the anti-fog elements buried in the laminates of the glass, which would in theory allow operators to remove the component and save weight.

However the acrylic version needs a hot air vent similar to automobile defoggers, cancelling out the weight savings gained by moving to the stretched acrylic windscreen. Askue doesn't know of any operators who have ordered the stretched acrylic replacement.

Glass windshields remain popular however -- Askue says the company has logged 5 million flight hours with no windscreen breaches.

In one case, an operator in Florida hit a turkey vulture at 155kt cruise speed. Though the windscreen was "starred" Askue says "nothing penetrated" into the cockpit. The jolt of the hit however did knock the throttles (see location in picture below from Ed at Picasa) out of the detent position, requiring pilot attention.

Later, Aeronautical Accessories developed and earned FAA certification for a cast acrylic aftermarket windscreen that was lighter than the stretched acyrlic, a plus from a cost-benefit standpoint in that the helicopter could carry that much more payload.

The penalty, we are learning, is that it is not as strong as the others, in part because there was no requirement that it should be.

"Available test data for this material indicates a lower level of impact tolerance as compared to glass or stretched grade acrylic material," says Sikorsky in the all-operators note, or more to the point, the cast acrylic windscreen can offer the equivalent protect if speeds are kept to 109kt or less.

From a KE perspective, that means the cast acrylic can handle 1,572 Joules (1 kg traveling at 109kt). 

Hitting a 1kg hawk at 138kt would have generated 2,520 Joules, 60% more than the windscreen could handle, if you believe Sikorsky's numbers.  

The strength difference is inherent in the build process of the two acrylics. Sikorsky notes:

...Acrylic windshields are commercially manufactured for aviation applications in several grades. Cast grade material is cast to the final product thickness and thermally formed in a mould to the final contour. Stretched grade material is initially cast in a thicker section and subsequently reduced in thickness via mechanically stretching the material while heated.This stretching process improves the mechanical properties of the resulting product, in particular, the impact tolerance and fracture behaviour...

No one will ever mistake Frank Robinson's helicopter factory for a six-sigma "lean" assembly line regardless of how prolific its output.

Lean lines are generally so efficient, synchronized and hushed that your eyes deceive you into thinking that not much work is being done.

Robinson's 1,300 employees toiling away in two cavernous manufacturing buildings in Torrance, California, however belt out cacophony like the little Who boys and girls in Dr. Seuss's timeless Grinch tale.

"...They'd rush for their toys! And then! Oh, the noise! Oh, the Noise! Noise! Noise! Noise! That's one thing he hated! The NOISE! NOISE! NOISE! NOISE!"

Their toys in this California tale are rivet guns, metal presses, paint booths. Their product starts as raw metal coming in one door; It ends as a two-seat or four-seat helicopter coming out the back door. Much noise in-between.

The only items not made in-house are fibreglass, instruments, engines (they're made by Lycoming) and the honeycomb sandwiched between two metal skins of each helicopter's rotor blades.

Given the economy, not as many helicopters are coming out the back door this month as in months past, but officials hope for a rebound when financing frees up and a new helicopter, the R66, is ready for mass consumption.

Last year's production numbers, which saw a record breaking total of 893 helicopters produced, amounted to about 20 helicopters built per week - a combination 17 four-seat, fuel injected R44 Raven IIs, 4 two-seat R22s and 3 normally-aspirated R44 Raven Is. Each takes about 8-10 weeks complete and 70% of all helos made at Robinson get exported.

Mixed in with the new builds are overhaul projects. All Robinson helicopters have to be overhauled by an authorized service centre or the factory every 12 years or 2,200 hours, costing about 60% of what a new helo costs. A new standard-equipped R22 costs about $250,000 while; a new R44 Raven II runs about $400,000.

Once built, each helicopter shows up in the flight test room, where it gets two rotor blades installed, tracked and balanced and where batteries are placed. Police and electronic news gatherers have the batteries placed in the tail cone while others have the battery under the engine or the seats.

Lastly flight test pilots spend 4 hours ringing out every new helicopter, after which the aircraft undergoes a final detailing and inspection.

When I toured the facility on 24 February, Frank Robinson waited in a room near the flight test area with his new million-dollar baby. The R66 is the company's first turbine-powered helicopter and its largest aircraft to date.

Powered by a Rolls-Royce RR300 turboshaft engine, the R66 holds five passengers (2+3) and will have the first baggage compartment in the portfolio. Robinson has not yet set the price, but hints that it will be in the neighbourhood of $1 million.

Frank Robinson is pictured below with N266RH, the second R66 prototype and part of the FAA certification program, which is expected to be complete next year.