A-6E Intruder crash and ejection

Posted on 01. Dec, 2008 by in Featured

I saw a copy of this tape with a question on what went wrong. The two most likely causes are “two blocking the gear” or a cross deck pendant failure. They ultimately end up being the same result with different causes.

First- two blocking the gear: An aircraft carrier’s arresting gear mechanism is mostly below deck. On the flight deck what shows is the cross deck pendant or arresting cable; it is attached to two longer cables that come up from the arresting gear room. These cables are threaded through a giant block and tackle type machine. As the cable is pulled out on the flight deck the blocks are pulled toward each other. The rate they are allowed to come together is regulated by a hydraulic reservoir and throttle. As the blocks come together they push large pistons into the reservoir forcing hydraulic fluid through an opening. This opening is set at different sizes allowing the amount of fluid and thus energy absorption to vary. This is necessary because aircraft vary in weight; for example an EA-6B Prowler weighs approximately 45,000 pounds when it traps aboard (arrested landing) the aircraft carrier. A TA-4J Sky Hawk traps aboard at approximately 14,000 pounds. By varying the opening in the hydraulic throttle they can recover one right after the other (EA-6B small opening/more resistance TA-4J larger/less). It is critical that the correct weight is “dialed” in. If the TA-4J weight is dialed in (or no weight at all) and an EA-6B lands the cables will feed out but the resistance will not be enough to bring the heavier aircraft to a stop; thus all of the cable will play out until the blocks are pulled together to the stops. That is called “two blocking the gear”. Once that happens there is no elasticity in the system and something has to give. Normally that is the cross deck pendant, it parts (breaks). The result is that the aircraft is decelerated below flying speed then let go by the parting wire. Unable to fly or stop the crew pulls the ejection seat handles.

Second-Is a straight cross deck pendant failure. The pendants take a pre-determined number of “hits” then are replaced. They don’t always make it to that number; sometimes they fail pre-maturely. The result is the same as above. It also is extremely dangerous for anyone working on the flight deck as it swings like a scythe.

It could also be the hook spitting the wire; which means the hook works itself free. Again the same result. Another possibility is spearing the wire, actually separating the strands and only grabbing a percent of the strands that then fail under load. These failures are all very rare.

Another note: the A-6 did make it back into the air. It is easy to say the crew panicked; however IMO the more likely explanation is that the combined weight of two men, in 35 pounds of flight gear and two ejection seats lowered the weight of the aircraft enough for it to claw its way airborne. Also the weight came out of the front of the aircraft shifting the center of gravity aft, causing a rotation moment. Naval Aviators always go to full power when they touch the deck and don’t pull it back until stopped. So the throttles were still at 100%. Part of the daily brief is; “if we spit the wire and don’t have X amount of knots, eject!” The best news is both Pilot and BN (Bombardier/Navigator) got out.

Leave a Reply