U.S. Air Force CV-22 Osprey tilt rotor aircraft crashes on Eglin range

Jun 14 2012 - 1 Comment

A U.S. Air Force CV-22 Osprey, belonging to the 1st Special Operations Wing, of the Air Force Special Operations Command, crashed at around 18.45 LT on Jun. 13, 2012, on the Eglin Range, north of Navarre, Florida.

Five crew members aboard the tilt rotor aircraft were taken to local area hospitals. Two of them were taken by ambulance, while the other three were taken via air.

According to the first reports, the Osprey was involved in a routing training mission with another aircraft of the same type, when it crashed for reasons that a board of officials will investigate. An AC-130 flying nearby was spotted circling above the crash area to provide on-scene coordination of the rescue ops.

About two months ago,a U.S. Marine Corps MV-22 Osprey crashed in southern Morocco. Two marines were killed and two other severely injured in the crash on the VMM-261 tilt rotor aircraft involved in African Lion joint exercise.

On the same day, another Air Force Osprey performed a successful emergency landing in a field in Amarillo, because of a faulty indicator light: the CV-22 was flying a test flight when the light prompted pilots to land near Greyhawk Landing. Fortunately, no one was hurt and the tiltrotor was not damaged.

Although both the Air Force and the Marine Corps consider the revolutionary tilt rotor absolutely safe, the accident rate of the Osprey raised some concerns (and much debate) in the recent past.

Image credit: U.S. Air Force

  • Rex Rivolo

    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.

    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. 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 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.

    Had TR-65 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 is 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. 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”

    This accident was clearly not caused by “Pilot Error”; 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.

    Finally, the findings of this AIB can only be explained as “politically motivated” (blame the pilots not the aircraft) and not based on the obvious facts.

    This is unconscionable and the USAF leadership should step up to retract this slander of dedicated, hard working, aircrews who sacrifice much to keep us safe.