The Project for Government Oversight has distributed a press release that flags the number of mishaps the H-47 Chinook has suffered as a result of “brownout.” Brownout refers to the pilot’s loss of ground reference created by the cloud formed due to the helo’s downwash. Generally, more downwash, bigger cloud. Here’s the release:
Brownout Accidents Plague CSAR-X Helicopter:
Controversy Surrounds Air Force Selection
The H-47 Chinook clocked only 7 percent of all U.S. Army helicopter flight hours between February 2003 and June 2005, yet accounted for 30 percent of all brownout mishaps between fiscal years 2002 and 2005, data from the U.S. Army shows. According to Aerospace Daily and Defense Report yesterday, “Congressional lawmakers are reviewing downwash data for the helicopters that competed for the U.S. Air Force’s combat, search and rescue (CSAR-X) helicopter replacement fleet to make sure rescue operations can be done safely.” As part of this review, Congress should also look at Army data which show that the Chinook disproportionately suffers accidents from brownout (swirling dust and sand) compared to the rest of the helicopter fleet.
Boeing’s H-47 Chinook helicopter was selected for the $10 to $15 billion combat, search, and rescue (CSAR-X) contract last year which required, but the contract is being re-bid in response to protests by competitors.
POGO recommends that the Air Force make a fair comparison of the bidder’s proposals on the basis of this and all the other key performance parameters, and that the comparison and standards for comparison be made as transparent as possible to the bidders.
CSAR-X program documents clearly state the need for a helicopter which does not have a rotor downwash that will impede operations. According to the June 16, 2005, Capability Development Document for Combat Search and Rescue Replacement Vehicle (CSAR-X)/Personnel Recovery Vehicle (PRV):
The downwash produced by the CSAR-X (PRV), at mid-mission gross weight, in and around the recovery vehicle during a hover in all operational environments must not impede safe and successful recovery of isolated personnel. These environments include, but not limited to, heavily forested steep mountainous, smooth-level, rough-level, smooth-sloped, and roughsloped terrain in calm and high crosswind conditions. Loose particles such as tree limbs, sand, snow, water or rocks in the hover zone at mid-mission gross weights with SCL in Appendix G must not prevent the Recovery Team or injured and un-injured isolated personnel from conducting safe AIE operations (providing emergency life saving measures to isolated personnel, placement of a non-ambulatory personnel in a hoist recovery device, overland movement, self protection, communication, and swimming). (Emphasis added)
According to POGO Defense Investigator Nick Schwellenbach, however, “The Air Force seems to have ignored its own requirement when it picked the Chinook.”
Despite the rotor downwash requirement, the initial competition picked a helicopterBoeing’s Chinookthat produces significant downwash, and is prone to accidents due to brownout (swirling sand and dust caused by downwash). According to the May 2005 article “Brownout on the Battlefield,” in FlightFax, a magazine by the U.S. Army Combat Readiness Center,
In the past 5 years, there have been 11 Class A, B, and C aviation accidents involving Chinook aircraft with brownouts being the trigger event. These mishaps have resulted in 16 non-fatal injuries and equipment damage costs in excess of $37 million.
A look at data compiled by the U.S. Army shows that the Chinook disproportionately suffers from brownout, and other mishaps and accidents when compared to the overall U.S. helicopter fleet.
– Ward
Don’t all helicopters of equivalent capacity produce the same downwash? F=Ma is not different for US101 than it is for the Chinook.
Cranky
Interesting work. Now I’m not an advocate or dissenter of the chinook but a few questions come to mind; 1) what are the mission profiles flown by other aircraft? they may not be in environments or conditions where brownouts could occur. 2) are there any TTPs that would cause more brownouts on chinooks than others? could be a time for TTP improvement vice an indictment of the a/c. 3) do other a/c have equipment that helps avoid brownout mishaps that chinook doesn’t? 4) how often are missions executed when brownout is a potential condition?
I’m sure other folks will have some more, and the answers to those questions very well could further argue against the selection of the chinook and in favor of the 92 or 101. But let’s not be hasty and pick one stat/condition to make the case that any a/c is the right or wrong one. There are always pros/cons to any a/c and the strengths/weaknesses of those can be just as diverse as the persectives of the operators that use them.
Cranky,
Less mass and less acceleration would mean less force (which means less particles are provided with sufficient force to become airborne.
Cranky, I was originally thinking the same thing, but I figure that it’s a function of aircraft mass, rotor diameter, and lift profile over the length of the rotor.
Larger rotors should mean a lower velocity down-wash.
–Jeff
We could do what our “European Allies” do and only use little helicopters. Odd how our “European Allies” are functionally dependent of US CH-47s in Afghanistan because of that darn OGE hover ceiling on little helicopters. But hey look at the bright side of abandoning injured soldiers or troops that run out of ammo because your wimpy helicopters can’t fly the mission: You’ll have fewer damaged helicopters. And who would say that isn’t worth it?
+1 to Kevin’s comments
Kevin, this Dutch “European Ally” does fly the Chinook in Afghanistan (and we did in Iraq) together with our own Apache-Deltas and (French-made) Cougars.
We lost one Chinook due to brown-out in Afghanistan, and using small, medium or huge helos doesn’t really make a difference: even a small brown-out can be dangerous.
Question is which helo is the best insertion/extraction a/c, and counter the brown-out (or white-out during winter ops, equally hazardous) with good training and even better crew coordination — better a good crew chief than a supa dupa (expensive) helo.
Rotor downwash aerodynamics is a difficult subject and is not dependant only on mass/acceleration of the aircraft. The fact that the helicopter blade is designed as a compromise between hovering and going fast also plays a large role.
The only helicopter that seems to do well with this is the Merlin, which seems to create a distant “brownout” cloud, so the pilot can still see the ground.
Anyways, I doubt the findings of this report.
To be able to state that CSAR-X choppers are more susceptible they would have to make sure all helicopters operate in the same environment.
CSAR helicopters always operate in harsher environments and will often have to land in unknown areas and where hostile forces will also be present — meaning that you are also coming in faster.
It’s always possible they could put different blades on the chinook to improve the brownout condition. Since the CSAR mission doesn’t require the ability to lift as much they could use a different airfoil shape.