Airbus Tanker Wrong for Airforce

In the next few weeks the Pentagon will, for the third time in a decade, release the final request-for-proposal (RFP) for the $35 billion KC-X contract for 179 airplanes to replace the Air Force’s aging KC-135 tankers, a fleet of modified Boeing 707s dating from the era of President Dwight D. Eisenhower.

The bidders for the KC-X contract are the European Air Defense Systems-Northrup Grumman consortium offering the French Airbus A-330 tanker and Boeing’s tanker version of the 767 airliner.  Industry rumors say Boeing may also offer its larger 777 airliner in a tanker version.

HUMAN EVENTS has raised many so far unanswered questions  about the A-330’s suitability for the Air Force tanker mission because several of its physical characteristics — and its ability to reach needed speeds and perform critical maneuvers — make it incapable of flying the mission.  

Our continuing investigation into the A-330 has revealed two new grave concerns. First, the Airbus seems to be unsafe at any speed due to a design defect in the aircraft’s tail. Second — and as a direct consequence of the first — the onboard computer system is governed by programming “laws” which make it impossible for the pilot to make the aircraft perform combat maneuvers, creating an apparent high flight-safety risk.

In the wake of several fatal Airbus crashes involving the in-flight loss of the vertical tail fin Airbus added the following warning in the limitations section of the A-330 flight manual:

“WARNING: Rapid and large alternating control inputs, especially in combination with large changes in pitch, roll or yaw (e.g. large sideslip angles) may result in structural failures at any speed.”

On November 12, 2001 an Airbus 300 — which has the same tail design as the A-330 — crashed in Queens, New York killing all aboard. The investigation determined that the tail literally broke off the aircraft shortly before it hit the ground, According to a 2004 Washington Post report on the NTSB investigation of the craft said, “Airbus said that the pilot’s aggressive back-and-forth use of the rudder right after Flight 587 encountered wake turbulence led the tail of the aircraft to come off.”  

In June 2009, an A-330 Air France flight from Brazil to France crashed, again killing all aboard.  Reports of the debris found by search and rescue forces show that the tail section was found miles from the main fuselage wreckage, indicating it had separated from the aircraft shortly before the crash.

EADS/Airbus appears to have some concerns about the structural strength and integrity of the A-330’s composite tail. The Maneuvers and Procedures section of the flight manual notes that “other than normal use of the rudder, rudder reversals and sideslip angles,” (i.e., including those necessary requirements for the close formation flying required to refuel combat aircraft), “may be beyond the structural design limits of the airplane … certain combinations of sideslip angle and opposite rudder deflection can result in potentially dangerous loads on the vertical stabilizer.”

In Air Force tanker operations, pilots have to make sharp turns and climb or dive without a second’s delay.  Those maneuvers could cause the A-330’s tail section to break off.  

And that’s not all.  On most aircraft — including the Boeing 767 and 777 — the computer controls including the autopilot instantly disengage when the pilot grabs the controls and takes control of the aircraft. But not on the A-330.  The pilot has to first disengage the autopilot manually before the stick and throttles (and rudder controls) let him take control.  The time that takes may mean the difference between a safe maneuver and a mid-air crash with the aircraft being refueled.

A second question relates to the compatibility of the computer-controlled flight systems used by Airbus with the United States Air Force’s specific requirements. On the Airbus A-330, the computer flight control laws are designated Normal, Alternate and Direct control. Under Normal Law, five control computers, three primaries and two secondary, electronically interpret the pilot’s inputs to a side control stick and conventional rudder pedals and actuate hydraulic three-axis flight control surfaces including the rudder, elevator, ailerons and spoilers.

Normal law operations will not allow the pilot to:

•    Exceed the airplane’s load limits of 2.5 positive Gs or 1 negative G.
•    Exceed pitch attitude parameters of 30 degrees nose up or 15 degrees nose down.
•    Exceed a bank angle of 67 degrees.
•    Exceed the maximum angle of attack of the wing.
•    Exceed the maximum airspeed/Mach number.

Airbus’s side control sticks operate independently and there is no feedback on the second pilot’s controls other than instrument indications. In the event that both pilots make control inputs, the computer mathematically sums those inputs and moves the flight controls accordingly. This means that if one pilot moves his side control stick to full left deflection and the other pilot simultaneously moves his stick full right, the airplane will not bank in either direction and will instead maintain level flight and warnings will sound in the cockpit. There is a priority override button on each side stick. Whichever pilot last pushed the button will have command of the airplane — unless the other pilot hits the button on his side again. This means that in a tense situation requiring immediate action, whether in training or combat, aircrew coordination can be hampered by that lack of control feedback and the addition of visual and aural warnings.

The Airbus flight manual warns against simultaneous pilot inputs in any flight mode. In general, failure to heed the warnings contained in a certified aircraft flight manual puts the airplane, its crew and passengers in danger. Pilots, both military and airline, interviewed for this article agreed that if Normal Law limits on aircraft performance are in place, tanker crew’s lives will be at risk.

Alternate Law is engaged solely by the flight control system if computer failures are detected. Many of the Normal Law protections are lost or degraded in this mode and since the computers cannot be trusted, the system will not revert to Normal Law controls.

Additional system failures cause the computers to shift to Direct Law. Pilot control inputs are translated directly to the aircraft’s control surfaces with none of the protections of Normal or Alternate law modes.

Should a severe in-flight upset or unusual aircraft bank or pitch attitude occur that exceeds the Normal Law parameters the system goes into Abnormal Alternate Law mode for the remainder of the flight. In these degraded modes it is conceivable that the airframe could be damaged or lost to structural failures caused by pilot inputs.

As a last resort in the event of a complete loss of the flight control system, the Airbus goes to Mechanical Backup mode. Pitch, the angle of the nose above or below level flight attitude is controlled by a manual trim wheel. Bank, the angle of the wings from level, and the rate of bank are controlled using differential power from the engines. Yaw, the horizontal movement of the aircraft’s nose during a turn, is controlled by the rudder pedals. The rudder is attached to the vertical fin on the tail that was notably lost in flight before the A-300 crashed in New York in 2001 and the A-330 that crashed into the Atlantic last June.

An airline pilot who regularly flies Airbus aircraft and used to fly tankers in the USAF Reserve said a “pilot flying an Airbus in Mechanical Backup mode is having a bad day that isn’t likely to end well.”

There are distinct philosophical differences between the Airbus and Boeing’s fly-by-wire flight control systems throughout all phases of the flight envelope. Those differences could be the distinction between a tanker returning to base or being lost in action. The web sites, and offer an in-depth view of the Airbus systems.

With the Airbus’s computer laws in effect, the A-330’s “envelope protection system” physically prevents the pilot from performing emergency overtake, breakaway, or evasive action maneuvers that exceed computer-determined parameters. The Airbus will not perform maneuvers that require steep angles of bank, steep nose up or down pitch angles, or airspeeds above or below maximum/minimum speeds to get out of harm’s way. Such maneuvers are possible in all other USAF tankers and the Boeing 767 tanker.

A retired USAF general, familiar with tanker operations and the RFP process, questioned the advisability of the U.S. relying on France and other European nations to manufacture components for the EADS/Airbus tanker for shipment to Alabama for assembly. Our pilots risking life and limb on the front lines of combat need new tankers from a supplier that will not be affected by foreign politics. Should one of those foreign suppliers take umbrage with U.S. and refuse to deliver tanker components, America’s military capability around the world would suffer. Monday, France accused the U.S. military personnel sent to earthquake stricken Haiti of being an “occupation” force.

There is an increasingly limited supply of leftover 707 airframes the military has been buying to keep the KC-135s flying. At present, between 25 to 30 percent of the KC-135s are out-of-service for major maintenance. As replacement parts become scarce that number will increase and more KC-135s will be permanently grounded.

President Eisenhower once warned of a military-industrial complex influence on this nation’s defense strategy. Today, with the USAF urgently in need of replacements for airframes that date from the same era as the outgoing president’s warning, foreign politicians and businesses are the congressional-industrial complex trying to influence our military’s defense planning. They are attempting to sell the United States a potentially unsafe aircraft that fails to fulfill the Air Force’s requirements. The pilots, officers and airmen who operate the military tanker fleet recognize that the Airbus A-330 is unsuited for the role and want the contract to go to a manufacturer based on the right choice — not politics and influence.

Putting aside the EADS/Airbus ultimatum that the Air Force modify the RFP to favor the A-330; the WTO’s ruling on the company’s illegal government subsidies; the history of political gerrymandering and financial bid-rigging that tainted past RFPs; time to delivery of operational tankers; the fact that fewer large tankers means fewer booms in the sky when aircraft need fuel; aircraft performance capabilities and the immense construction costs of upgrading the airfields to handle the overly-large Airbus A-330; there are two other valid reasons to reject the Airbus A-330.

The unresolved problems with the Airbus tail fin coupled, the incompatibility of the Airbus computer flight laws with actual combat conditions, coupled with the fact that the A-330 tanker cannot refuel all the U.S. aircraft in use clearly demonstrate that the EADS-Northrup Grumman aircraft is the wrong plane for the USAF tanker fleet.