Douglas DC-6 accident at Newark, New Jersey, 21 May 1951 (N-90896)

Accident narrative

At approximately 0408 on May 21, 1951, a National Airlines Douglas DC-6, N-90896, made premature ground contact in a swamp 1,800 feet short of Runway 6 while executing an instrument landing system (ILS) approach to Newark Airport in New Jersey. The captain applied full power almost simultaneously with the impact, and the aircraft became airborne again, completing a landing on the airport. None of the 22 passengers or four crew members were injured. The aircraft sustained moderate damage when its left stabilizer struck a steel pipe supporting a ground control approach (GCA) reflector.

### The flight

National Airlines Flight 486B was a return trip. The southbound flight from New York had originally been destined for Norfolk, Virginia, but diverted to Richmond due to poor weather. The same aircraft and crew departed Richmond for Newark at 0258 on May 21. The aircraft's gross weight was 77,160 pounds, well within the allowable maximum of 81,400 pounds, and was properly distributed. The captain had logged 8,273.20 flying hours, including 723 hours in DC-6 equipment, and had recently received an "Above Average" grade on ILS approaches during a company flight test.

Airways Route Traffic Control cleared the flight to Newark on an instrument flight plan. Over New Brunswick, Newark Approach Control cleared the flight for a straight-in ILS approach to Runway 6 and advised that GCA would issue advisories on the 110.3 megacycle localizer frequency. The weather at Newark was reported as an indefinite 300-foot overcast ceiling, three-fourths of a mile visibility in fog and smoke, and an east-southeast wind at 10 to 15 miles per hour. These conditions were above National Airlines' minimums of 200 feet and one-half mile.

### The approach and accident

The captain, who was flying, stated that the glide path was intercepted and landing checklists were completed. At about six miles from the airport, the GCA operator instructed the flight to "Transmit 118.3." The captain stated he misinterpreted this to mean GCA would transmit its advisories on 118.3 megacycles rather than the usual 110.3. Because of this misunderstanding, the crew did not utilize GCA to check the accuracy of their approach. The GCA operator monitored the final six miles without knowing the flight was not receiving the information.

A transcription of the GCA advisories showed the aircraft was slightly to the left on the glide path at times. At one mile from touchdown, the transcription showed the flight low and to the left. The GCA operator stated the aircraft then disappeared from the elevation scope between the middle marker and the runway.

The captain advised that his cross-pointer indicators reflected a normal approach. Passing over the middle marker, which is 0.61 miles from the runway with a 220-foot glide path, the captain said his altitude was approximately 240 feet and indicated airspeed was about 135 miles per hour. The copilot, who had been instructed to seek visual reference, advised that the approach lights could be seen to the right. The runway and approach lights were on full brilliance.

The captain stated he leveled the aircraft off at 200 feet by applying rearward pressure on the elevator control, looking out to check the lights. The aircraft was descending at approximately 550 feet per minute with landing gear down and 30 degrees of flaps. No additional power was applied. Seeing the approach lights well to the right, the captain stated he elected to execute a missed-approach procedure. He immediately returned his attention to his instruments and applied full power. Almost instantaneously, the aircraft made forceful contact with the ground. The copilot stated he saw the ground coming up rapidly and also applied full rearward pressure and reached for the throttles, but the captain was already applying power.

The touchdown occurred in a swamp in an approximately level flight attitude, to the left of the approach lights centerline. The first evidence of contact was a swath cut in swamp grass seven to eight feet high, 45 feet prior to touchdown in the mud. The wheels sank up to 12 inches into the marsh, leaving marks 126 feet long. The outer edge of the left stabilizer struck a 2-inch steel pipe standing 85 inches high, striking it 58 inches above the ground and shearing off about three feet of the elevator. The aircraft immediately became airborne again and made a tail-low landing on the airport, coming to rest 1,215 feet from the approach end of the runway and 110 feet to the left of the runway edge.

### What the investigation found

The Board investigated the weather in the swamp area and found conditions were not favorable for important differences from the airport observations.

Numerous ILS approaches made by other aircraft both before and after the accident showed that all ground components of the ILS and GCA systems were functioning normally. A CAA flight check the following day found all elements within tolerances. When the CAA flew over the simulated flight path directly above the wheel marks in the swamp, the localizer indicated about three-fourths of a full deflection to the left, and the glide path altitude at that point was 12 feet.

The aircraft was repaired and test-flown two days after the accident. No malfunctions were found in the airborne equipment, radio receivers, altimeters, or related flight instruments. The captain was unable to furnish a reason for the accident other than possible altimeter lag or instrument errors, but the investigation showed the altimeters were on the correct setting and functioning properly.

The Board noted that during relatively slow flight, increasing the angle of attack without adding power can result in decreased lift, increased drag, and a loss of airspeed and altitude. The Board concluded that the captain exercised faulty judgment and incorrect piloting technique by not adding power in coordination with the up elevator when he leveled off. The Board noted that a serious accident was averted only by the timely application of full power an instant before striking the marsh.

The Board considered the lack of GCA advisories to be of secondary importance, noting that GCA is an adjunct to the ILS and that the captain could easily have clarified the radio misunderstanding. Following the accident, National Airlines revised its pilot training to stress that a missed approach is mandatory if the aircraft is not in the proper position on the ILS at the middle marker.

### Probable cause

On the basis of all available evidence, the Board determined that "the probable cause of this accident was faulty judgment and improper piloting technique on the part of the captain while executing an ILS approach, resulting in forceful contact with the ground prior to reaching the airport."