The Air Force Special Operations Command has released the results of the investigation into the Jun. 13, 2012 accident of a CV-22B. The tilt-rotor aircraft, which was assigned to the 1st Special Operations Wing, was flying in a two ship formation when it crashed at approximately 6.45 pm local time during a training mission to the north of Navarre, Florida on the Eglin Range.
All five of the 8th Special Operations Squadron aircrew were seriously injured but none suffered life threatening injuries.
The AFSOC, commander convened an Accident Investigation Board to investigate the crash and the circumstances surrounding it and designated Col. Hans Ruedi Kaspar, 23rd Air Force vice commander as the board president.
The Accident Investigation Board President released his findings and said that there was clear and convincing evidence that the cause of the crash was the crew’s failure to keep the aircraft clear of the lead aircraft’s wake. The result of this was an “uncommanded” roll to the left along with a rapid loss of altitude which resulted with an impact with the terrain.
The aircraft was destroyed upon impact with the loss valued at approximately 78 million USD.
Although Pentagon press secretary George Little speaking to reports recently said: “The Osprey is a highly-capable aircraft with an excellent operational safety record, which includes more than five years of worldwide deployments and 140,000 flight hours,” the safety record of the tilt rotor aircraft, in spite of the DoD, Air Force and Marine Corps claims, has been much debated in the recent past.
Even the loss of a U.S. Marine Corps tilt rotor aircraft that crashed in Morocco during African Lion joint exercise, with two marines killed and two other severely injured in the crash, and few other safety occurrences (that got a special attention on media attention even though they were quite normal) contributed to fuel concerns in those who believe the aircraft is unsafe.
Among them there is A. Rex Rivolo, who is Chief Technology Officer of an aerospace corporation in Virginia, has seventeen years experience in DoD Test and Evaluation community as senior advisor to the Office of Secretary of Defense and served as the principal analyst for the MV-22 and CV-22 at the Institute for Defense Analyses (IDA), a nonprofit organization paid to do independent research for the Pentagon.
Rex has some strong credentials: he was a pilot for six years at the US Air Force and 22 years at the Air National Guard. He has some 7,500 flight hours in both tactical fighter planes and helicopters, including 531 combat missions with the F-4E Phantom in Vietnam. He has earned 5 Distinguished Flying Crosses, 28 Air Medals.
“The findings of the Accident Investigation Board (AIB) for the CV-22B, tail number 06-0032, crash on 13 June 2012 are a total distortion of the facts and a blatant attempt to blame the pilots for a very serious design flaw in the V-22 aircraft” he told The Aviationist.
The serious safety concerns over the V-22 response to interactions with proprotor wakes of another V-22 were raised as early as 1996 when pilots began reporting incidences of uncommanded roll during flights of multiple aircraft.
“I personally observed several instances of this while flying on the V-22 in the late 1990s as an observer supporting the Pentagon’s Director, Operational Test & Evaluation (DOT&E) during the V-22 operational test period. In their desire to meet cost and schedule milestones, these concerns were given little attention by Bell-Boeing and the USMC management team and they consequently mounted a strong campaign to discredit these concerns with DOT&E. This effort, supported by some of the world’s best aeronautical engineers and pilots convinced DOT&E that the problem was indeed minor and the concerns were overblown.”
“Following the 2000 crash at Marana in which uncommanded roll due to wake intrusion was a possible contributing cause, I recruited Professor Gordon Leishman, one of the world’s top rotorcraft scientists, to investigate the phenomenon using numerical simulation” Rivolo told The Aviationist.
The result of these calculations clearly indicated that V-22 rotor wake intrusion could be a serious hazard to V-22 because of the side-by-side design: “Based on these concerns, I succeeded in resurrecting the issue with DOT&E and the Director demanded that a test and evaluation program be designed and executed to quantify the seriousness of the phenomenon.”
“This test and evaluation program, known as Test Request 65 (TR-65), was designed by DOT&E, Bell-Boeing and the USMC. The TR-65 document, dated 9 June 2000, described over 23 pages of test sequences to be performed to evaluate proprotor wake interactions in the V-22. Eighteen months later, TR-65 was scrapped based on the then current flight experience in which no uncommanded rolls were experienced in the aircraft during formation flight. Based on a strong Bell-Boeing and USMC push to dismiss a “non-issue”, DOT&E acquiesced and TR-65 was never completed.”
As a consequence, the pluri-decorated former combat pilot says, the CV-22 Flight Manual, known as the “Dash-1”, contains only minor guidance in Section V (Operating Limitations) on formation flight position to avoid wake intrusion.
Rivolo believes that if TR-65 had been executed to completion, the uncontrollable rolls experienced by V-22 when intruding into another V-22 wake would have clearly been demonstrated along with the dangers of the phenomenon.
The entire text from Section V of the Dash-1 regarding formation flight limitations Rivolo sent us reads as follows:
FORMATION FLIGHT LIMITATIONS
1. VTOL/CONV mode formation flying requires a
minimum cockpit-to-cockpit 250 ft separation and 25 ft
step up; step up is to be maintained all the way to landing.
The requirement for step up is designed to prevent
asymmetric wake interactions caused when one rotor
on the trail aircraft encounters the wake of the lead aircraft.2. During APLN mode formation flight, maintain a
minimum cockpit-to-cockpit separation of 250 ft along
the bearing line. With less than 50 ft step up/down,
avoid lead aircrafts’ 5-7 O’clock.
“There are “Cautions” or “Warnings” throughout the Dash-1 concerning serious flight safety issues in various phases of flight but none on wake intrusion – a phenomenon that can result in an uncontrollable roll and consequent crash. This would certainly seem to warrant a “Caution” or a “Warning” within the Flight Manual.”
Rivolo says that as a consequence of the nonexistent TR-65 test results, the Dash-1 seriously underplays the significance of wake intrusion in V-22.
“It is noted that the Formation Flight Limitations in the Flight Manual only address a “minimum” separation; once outside that separation pilots can “legally” fly anywhere they wish in proximity to other formation aircraft. Unfortunately, the aircraft wakes remain active well outside this minimum separation and pilots can fly into them with catastrophic results. That the pilot was well outside of the minimum spacing limitations for formation flying is verified by the AIB in their Report which states:
“Although the MC did not maintain the required 25 feet of vertical separation from the MLA, the MA was two- to three-times the 250 feet and 375 feet distances referenced above and still encountered the MLA’s wake”
Rivolo believes the accident was clearly not caused by “pilot error” but it was the direct result of a basic design flaw in V-22 – the side-by-side rotor configuration and its susceptibility to rotor wakes.
“This accident will happen again and again,” he says.
Richard Clements contributed to this post.
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- Farnborough 2012: Boeing MV-22B tiltrotor aircraft attracts spectators as Marines claim “human factor” caused Osprey crash in Morocco (theaviationist.com)
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