“Everybody was on pins and needles trying to figure how the metal wing would test out with a salvo release – if the composite wing looked like it did.”
Wieringa and Wheeler launched from Pax River for a practice run on a very cold February day. Climbing to 40,000 feet, they set up on an east-west course over the Chesapeake Bay off the air station.
“We rolled inverted and pulled into a 60-degree dive. The test point called for release at about 12,000 feet AGL (above ground level)at 550 knots and .5 gs. We were going downhill at full power but we weren’t fast enough. So I climbed up to 40,000 feet and tried again. We rolled over and into the 60-degree dive. This time we were 25 knots too slow. We tried a third time, then finally gave up.”
We climbed up to 40,000 feet to make the first run, and sure enough, I beat the target airspeed by five knots. So we agreed that we were ready to go for real on a live run.
Wieringa was puzzled as to why the A-6 couldn’t reach 550 knots. Wheeler had the answer: It was too cold.
“I said, ‘What do you mean it was too cold?’” Wieringa said. “Wouldn’t the engines be producing more power?”
Wheeler replied that the dense air-producing cold weather along with the draggy design of the Intruder’s engine inlets and the area behind its canopy likely kept the airplane from reaching the target speed.
With temperatures climbing into the 40 degree Fahrenheit range, the test was rescheduled later that week.
“Ladd did the math again and said, ‘We’re gonna make it by five knots.’ We climbed up to 40,000 feet to make the first run, and sure enough, I beat the target airspeed by five knots. So we agreed that we were ready to go for real on a live run.
“We set up on heading, rolled over, and pulled to 60 degrees. The airplane accelerated nicely and then at about 1,000 to 2,000 feet above the target altitude, it started un-commanded pitch oscillations.
“My eyes were as big as saucers! That had never happened to me before, and I had over 2,000 hours in the A-6 at the time. We had five stations selected, the master arm was ‘on’ and ‘salvo’ was selected. I got into the flight control-loop and stopped the pitch oscillations. The g-meter in the center console is about four inches in diameter. That made hitting the required g easier. The dive angle was good, the airspeed was good, and the g was right.
“I pickled the bombs and there was a big bang! Probably the biggest bang I had ever felt, and I had a lot of experience with weapons separation.”
The simultaneous release of the five 2,000-pound Mk. 84s caused “g-jump,” Wieringa explained.
“Basically, the ‘jump’ was the difference in the angle of attack of the airplane with bombs and then without them. Combine that with the .5 g we already had on the airplane, and the result was a plus-9g hit to the cockpit and a 21g hit to the tail!
“When we watched film of the release afterward, you could see the tail visibly going up and down by a foot of travel. But it wasn’t perceptible in flight. I just remember a big jolt to the cockpit. It happened really fast.”
Wieringa and Wheeler made a normal dive recovery with no drama – “the airplane felt fine.”
“We looked at each other and wondered what had happened. Then we rolled over on a knife edge to try and see what the impact of the bombs looked like. It looked nasty, because there was a big separation. That answered the question if there was any difference of the bomb separation between the composite wing and the metal wing. No, no difference.”
A post-landing inspection of the A-6 showed no damage. Wieringa reported the incident to Cmdr. Steve Hazelrigg, then the chief test pilot at Strike. After watching film of the test, NAVAIR was informed of the problem.
“There wasn’t any data to base a decision on from a performance and handling qualities point of view because the airplane was set up for the weapons separation test,” Wieringa noted.
“Maybe a month later, a test pilot named Kurt Schroeder [Grumman chief test pilot] was doing the same test. If my memory’s right, they had three or five TERS [triple ejector rack] on the A-6, making it very draggy. I was in the Range Control Center watching the flight.
“This was a rare event where you had to have a really high drag-count and really high mach speed. At really high drag-counts, the center of pressure of the wing would fluctuate symmetrically but rapidly back and forth. That’s what was inducing the pitch oscillations.”
“He gets to the test point, pickles the bombs, and it was ugly. They started bouncing off the underside of the airplane. They ripped right through the birdcage. The test conductor didn’t see it because it happened in a flash. I said, “Tell them to declare an emergency – multiple bomb-to-airplane collisions!”
Schroeder landed safely, and finally, Strike had the evidence it needed to discern what was causing the oscillations, Wieringa had experienced.
“This was a rare event where you had to have a really high drag-count and really high mach speed. At really high drag-counts, the center of pressure of the wing would fluctuate symmetrically but rapidly back and forth. That’s what was inducing the pitch oscillations.”
Wieringa left later the test program to work on the ill-fated A-12 program with NAVAIR. Meanwhile, the re-wing program was scrubbed.
This article first appeared in the NAVAIR: 50 Years of Naval Air Systems Command, 1966-2016 magazine.