The Marine Corps investigation into the crash of an MV-22 Osprey tilt-rotor aircraft May 17 in Hawaii determined that it was caused by dust stirred up by the rotor wash.
After making multiple attempts to land in brown-out conditions, the buildup of debris on the turbine blades and vanes led to a compressor stall in the left engine, which decreased lift and resulted in the hard landing and fire.
The report found that pilot performance and an improper site survey of the landing zone led to the accident, resulting in the deaths of two and injuries to 20 on board.
The potential for the Osprey to deliver water or personnel to fight wildfires was evaluated by the Marine Corps in tests with a 900-gallon water bucket. They recommended that the aircraft not exceed 90 knots with a bucket and 50 knots when dropping water.
The Osprey is a tilt-rotor aircraft capable of vertical or short takeoff and landing. When airborne, it can cruise at over 300 mph, can carry 24 to 32 troops, or 15,000 pounds of external cargo.
We have written several times about the tilt rotor MV-22 Osprey, and how it may or may not be suitable to fight wildfires by dropping water or transporting firefighters. While it can carry up to 15,000 pounds of external cargo, which might translate to about 1,500 gallons of water, the extreme rotor downwash and the heat from the exhaust which has started fires are two serious limiting factors.
Four MV-22s are being used in Nepal as part of the U.S. response to the earthquake. An article in Calcutta’s The Telegraph points out two issues that are limiting factors for assisting with the earthquake response.
The Ospreys, the Nepalese have seen, flatten or blow off the roofs of the weak houses of villagers while landing and taking off. “They also raise dust storms,” one pilot said.
The MV-22 can carry up to 20,000 pounds of internal cargo or 32 troops, but apparently are having trouble with the density altitude at the high elevations in Nepal.
In one high-altitude village ravaged by tremors, the sight of an Osprey gave much hope to residents who wanted to be evacuated. But the Osprey’s payload limitations meant that the aircraft could evacuate only three persons. Elsewhere, villagers have asked the Nepal Army not to send the Ospreys “because they take away the little that remains with us”.
The Marines have conducted some tests to determine how feasible it would be for the MV-22 Osprey to fight wildland fires. As you may know, the Osprey is a tilt-rotor aircraft capable of vertical or short takeoff and landing. When airborne, it can cruise at over 300 mph, can carry 24 to 32 troops, or 15,000 pounds of external cargo.
In March, 2011 the Marines tested the Osprey with a 900-gallon Bambi Bucket suspended from 50-foot and 100-foot ling lines attached to the rear cargo hook while flying at up to 90 knots. After the tests, they came up with the following recommendations:
Maximum airspeed with bucket empty – 90 KIAS
Maximum airspeed with bucket full – 90 KIAS
Maximum airspeed when dumping – 50 KIAS
Max angle of bank- 30 degrees AOB
Use of Automatic Release Mode is prohibited.
Bambi bucket should be positioned to the 6 o’clock position of the aircraft prior to takeoff or landing.
Aircrew shall continuously monitor load for oscillations or unusual load movement.
Eric, one of our loyal readers, sent us a link to an article that explores the use of the military MV-22 Osprey tilt-rotor aircraft as a firefighting machine. The Osprey can take off and land vertically like a helicopter, and then tilts the rotors to fly horizontally at 277 mph.
The article dismisses the use of the Osprey as a direct attack, water-dropping aircraft, primarily for the reasons we outlined in an article we wrote in 2010 (scroll down to see a reprint of that post). But it suggests the Osprey could be useful in other ways to support a firefighting operation.
Here is an excerpt from the piece at medium.com, published October 27, 2013:
“It takes forever to get to a rural wildfire. Let’s use the Osprey to shrink distance and get critical equipment to the front,” he says. “Expensive command and control gear could be quickly transferred from central depots to forward fire bases, and from there other transport would carry them the ‘last half-mile’ to the fire line.”
“The Osprey can reduce the response time for elite wild-fire fighters — smokejumpers or hotshot teams — getting ‘boots on the ground’ faster, with more gear, reducing the time it takes to initially attack wildfires,” Hooper says. “And there’s also the possibility of reducing the cost of initial attacks: more firefighters can qualify for descending a rope-drop than for jump school, at less cost per person.”
Specialized critical assets — too expensive to distribute widely — are another potential cargo. “Air traffic control can get very tricky over a disaster area. Deploying an air traffic control team or a ‘control tower in a box’ would be a perfect example of how the range and speed of an Osprey could … make a big difference.”
But an Osprey with its twin 22-foot rotors creates ferocious downwash, blowing debris around like shotgun blasts. “They need to go into a relatively clean landing zone and then get out—so they may be a better fit moving equipment [near] an impacted zone than, say, doing gritty work inside the disaster area,” Hooper proposes.
The MV-22 Osprey, a tilt-rotor, vertical take-off and landing aircraft, is replacing some of the Vietnam era CH-46E Sea Knight and CH-53 Super Stallion helicopters used by the Marine Corps. Since the disastrous wildfires in southern California in 2007, the U.S. Navy and the Marine Corps have had an agreement with Cal Fire making it possible to use their military helicopters on fires if Cal Fire is unable to handle the fires with their own aerial assets.
In July of 2008, CH-46E and CH-53E military helicopters made at least 574 drops on fires in California, delivering 217,000 gallons of water.
At first glance, the Osprey might seem like an excellent firefighting tool. It is fast (cruises at 277 mph), could haul 24-32 firefighters, and could carry 1,800 gallons of water externally. But it has never dropped a gallon of water on a fire and it is possible that it never will due to at least two potential problem areas.
As you can see in the photo above, the rotor wash or downdraft from an Osprey is extremely strong–far stronger than a conventional helicopter. Rotor wash from a helicopter can cause, and has caused, serious problems when the wind from the rotors spreads the fire in unexpected directions, sometimes doing more harm than good. Marines even worry that Osprey rotor wash may damage or destroy unrecorded archaeological sites in training areas.
According to a report from the Government Accountability Office, the rotor wash creates enough force to knock sailors and aircraft off a flight deck on a ship.
May CAUSE fires
The Osprey’s engines run extremely hot, so hot that the Navy is taking special precautions to prevent the engine exhaust from melting or buckling the aluminum decks of warships. A report from DARPA states:
The deployment of the MV-22 Osprey has resulted in ship flight deck buckling that has been attributed to the excessive heat impact from engine exhaust plumes… Navy studies have indicated that repeated deck buckling will likely cause deck failure before planned ship life.
DARPA has designed a “flight deck thermal management system” which would liquid-cool the deck from below or above while the aircraft are idling or launching. The military has put out a request for proposals for other permanent deck-cooling systems that could be retro-fitted or designed into new ships still on the drawing board.
Wildfire Today reported on May 30, 2009, that an Osprey made an unscheduled precautionary landing in North Carolina and started a 5-acre fire in a wet marsh. We wrote then:
Marines refueled the Osprey but according to WECT.com, upon taking off it “smashed into swamp mud, nose first”. During that takeoff attempt, heat from the engine exhaust started a vegetation fire which did some damage to the exterior of the aircraft.
A news release from the Marine Corp claims:
The grass fire was quickly extinguished by the crew chief, but caused an undetermined amount of heat damage to the aircraft exterior.
But Emergency Management Director Eddie King said the local fire department had to work through the night to extinguish a 5-acre fire, in an area infested with snakes and alligators, that was caused by the incident.
(UPDATE October 28, 2013)
On May 31, 2010 an MV-22 Osprey tilt-rotor aircraft being demonstrated by the U. S. Marine Corp at a Staten Island park near New York City injured 10 spectators when the rotor wash sent debris flying. More information.