More Alerts For GA Pilots
No matter how extensively you test on the ground, the proof comes in the air
If your auto mechanic doesn't get something quite right when making a repair to your vehicle, chances are good that you'll survive. Even if you're zooming along the highway when you discover that a fix wasn't effective, you'll likely be able to pull over and come to a safe stop (unless it was the brakes that were supposed to be fixed). With airplanes, however, your options for remedial action are more limited when mechanical problems surface. Pilots are wise to add extra preparation to the mix when preparing for an aircraft's first flight after maintenance. More attention than usual may go into the preflight, run-up and selection of an after-takeoff emergency landing site. When the first flight after maintenance ends in an accident, the NTSB is called upon to investigate.
Cessna 210
A Cessna 210 slid off the runway during a landing with its main landing gear partially extended at Henderson Executive Airport, Henderson, Nev. The ATP-rated pilot was the only person on board and wasn't injured. The airplane was substantially damaged. It took off from Henderson and had been airborne for about 45 minutes. Visual conditions prevailed for the Part 91 flight.
The pilot told investigators that the post-maintenance test flight was to confirm that the landing gear retraction, extension system and flap activation system functioned properly. The hydraulic system had undergone maintenance.
After takeoff, the pilot retracted the landing gear. After the gear was fully up, he selected gear-down. The gear started to extend, but only made it part of the way down. He then tried to recycle the gear to the up position, but it remained down, and both main gears remained partially extended. The pilot then tried to pump the main gear down using the emergency extension hand pump. That didn't work, and the pilot also found that the flaps wouldn't extend. The pilot advised ground personnel of the problem, and the airport emergency equipment was deployed for a landing attempt.
The pilot touched down with the nose gear fully extended and both main gears in the partially extended position. The airplane eventually slid off the side of the runway and came to a stop on uneven terrain.
The airplane's owner originally brought it to the maintenance facility because of a hydraulic leak. During troubleshooting, it was determined that the hydraulic power pack wouldn't operate the flaps with the airplane's engine running, and the emergency extension gear handle had excessive pressure against it after the engine was shut down. The hydraulic leak itself was traced to the overflow vent line from the power pack.
The hydraulic power pack was replaced with a used unit. Both a normal landing gear swing and an emergency gear extension check were conducted. During the testing, leaks were found at the hydraulic pack fittings. They were fixed by installing new seals in the fittings.
After the airplane was removed from the jacks, an engine ground run was performed in order to test the engine-driven hydraulic pump and operation of the flaps when powered by engine-driven pump hydraulic pressure. Then, the airplane sat for a couple of days to confirm that there were no hydraulic leaks.
The airplane was then taken up for a test flight. The landing gear retracted and the flaps operated normally, but the gear didn't fully extend. The pilot extended the gear using the emergency extension hand pump and landed uneventfully.
Then, the hydraulic pump was replaced with an overhauled unit. The gear and flap systems tested satisfactorily on the ground. After that, the airplane went on the accident flight.
The hydraulic pump from the accident airplane tested satisfactorily. Although the hydraulic pack functioned properly in bench testing, there were discrepancies including valve leakage and wear, deformed O-rings and a fine black residue on some components.
The NTSB determined that the probable cause of this accident was an undetermined failure of the hydraulic power pack to fully extend the main landing gear through both the normal and emergency systems.
Convair CV-580
A Convair CV-580 crashed while attempting to return to the Rickenbacker InterÂnational Airport (LCK), Columbus, Ohio. The flight had just departed from runway 5L at LCK. The captain, first officer and an observer received fatal injuries. The Part 91 post-maintenance check flight was to end at Mansfield Lahm Regional Airport (MFD), Mansfield, Ohio. The airplane was on an IFR flight plan in visual conditions.
The airplane had been in for maintenance checks, which included flight control cable rigging. At noon local time, the flight received its takeoff clearance, and the takeoff roll began at about 12:03 p.m.
At 12:04, the crew contacted ATC and stated they needed to return. They were cleared to land on runway 5L. The controller asked the flight if emergency equipment was needed. The response was, "Negative." At that time, radar indicated the airplane was midway along in the downwind, at about 900 feet AGL. The ground speed was 171 knots. When turning to base leg, it had descended to about 187 feet AGL at 196 knots ground speed. The impact was about one mile southwest of the runway at about 12:06.
As part of the accident investigation, the elevator pitch control system was inspected. It was determined that the elevator pitch trim cables had been reversed, so that when the crew was trimming for nose-down, nose-up trim was being applied, and when they were trying to put in nose-up trim, the elevator trim system actually applied nose-down trim.
The NTSB determined that the probable cause of this accident was the improper (reverse) rigging of the elevator trim cables by company maintenance personnel and their subsequent failure to discover the mis-rigging during required post-maintenance checks. Contributing to the accident was the captain's inadequate post-maintenance preflight check and the flight crew's improper response to the trim problem.
Cessna 310
A twin-engine Cessna 310 was substantially damaged during a crash near Stotts City, Mo. The commercial pilot and the pilot-rated passenger were fatally injured. The Part 91 flight originated from the Monett Regional Airport (HFJ), Monett, Mo., and was headed to a private airstrip in Miller, Mo. Night visual meteorological conditions prevailed.
According to a witness, this was the first flight with a newly overhauled right engine. He said the pilots had originally planned the flight two days earlier, but postponed it because of discrepancies.
A mechanic who overhauled the engine reported that the pilot-rated passenger asked him if he'd fix the flat nose gear strut, and that he replied it would take at least a day to complete the repair. The owner told the mechanic that since he planned to fly the airplane to Ohio later that week for a corrosion inspection, he'd have it fixed then. He said that in the meantime, he'd fly with the landing gear extended because he was concerned the gear would get stuck in the nose well. As a temporary fix, the mechanic used shop air to inflate the nose gear strut.
During the preflight inspection on the day of the accident, the pilots noted the nose gear strut was flat again, and there was another discussion about keeping the gear extended for the flight. The two pilots boarded the accident airplane, started the engines and taxied toward the runway. The airplane stopped on the taxiway, and the engines were run-up three or four times. The pilots then taxied back to the hangar and shut the engines down. One said the right propeller wasn't "feathering" and needed to be fixed. The mechanic was phoned and asked to come out to the airport.
The mechanic said he was told that the right propeller control lever wasn't moving smoothly, and there was no mention that the propeller wasn't feathering. The mechanic asked one of the pilots to move the propeller control lever in the cockpit through its full range of travel. The mechanic said the arm on the propeller governor moved smoothly from stop to stop as the lever was moved. He told one of the pilots to adjust the friction lock for the lever, which eased the tightness of the lever. He also noticed the nose gear strut was flat again.
After the accident airplane departed, a witness took off in another airplane with the intent of following the 310 to Miller. He said that he established air-to-air radio contact with the other pilots and made visual contact. He said that the pilot-rated passenger radioed that "fuel or oil" was coming out of the right engine. The pilot-rated passenger subsequently radioed that they were losing oil pressure and were returning to Monett, followed by, "We shut the engine down." The witness responded, "Okay, I'll follow you."
The witness said he could see the airplane losing altitude and advised them that Interstate 44 was one mile ahead. The pilot then announced they were going to land on the interstate. The witness said he saw the light on the accident airplane's nose gear illuminate the trees in front of them. Then the nose of the airplane pitched up, rolled slightly to the right, and then pitched forward, followed by flames and a fireball.
Examination of the right engine revealed the oil filter adapter wasn't properly assembled or adequately secured to the engine.
The NTSB determined that the probable cause of this accident was the pilot's failure to maintain airplane control after he shut down the right engine in flight due to a loss of oil pressure. Contributing to the accident was the mechanic's improper assembly and installation of the right engine's oil filter adapter, which resulted in a loss of oil to that engine.
Peter Katz is editor and publisher of NTSB Reporter, an independent monthly update on aircraft accident investigations and other news concerning the National Transportation Safety Board. To subscribe, write to: NTSB Reporter, Subscription Dept., P.O. Box 831, White Plains, NY 10602-0831.
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