The winds of Pago Pago.

[Centaurus]

In the 1980's, Air Nauru 737-200's roamed the skies of the South Pacific. Its crews included a mixture of former RAAF and RAF, RFDS, Australian general aviation, and Australian Department of Civil Aviation pilots . Destinations were many and included Apia in Western Samoa and Pago Pago in American Samoa.

The latest isue of Business & Commercial Aviation (June/July 2020) had an article called Mountain Wave Monsters. Reading it brought back memories of a few mountain wave incidents I had experienced in my flying career. While I have never experienced severe mountain wave activity, there have been occasions where similar weather phenomena caught me unawares. One incident in particular was back in the Fifties when dropping supplies from a Lincoln bomber to a Tiger Moth pilot stranded on a remote island in the Whitsunday Passage group. The pilot had forced landed on a beach following engine failure.

The weather very windy and the small island had terrain about 1000 ft high. The wind was coming over the terrain at about 40 knots. We had just aligned ourselves on the lee side of the island for the run-in to drop stores, when one wing went down steadily and quite gently. . Despite full aileron,the wing kept dropping and I was forced to use differential power on the four engines as well as rudder to try and level the wings. The Lincoln was within 200 feet from the water before we regained level flight. To this day I cannot explain the reason for the wing drop but it was quite scary. We abandoned the exercise and left the Tiger Moth pilot to himself. A rescue boat arrived the next day.

Which leads me to the following accident and later incidents at Pago Pago and is the prime reason for writing this story. That is to warn charter or corporate pilots who may be unfamiliar with this remote part of the South Pacific that weather conditions can be tricky and need to be carefully monitored.

In January 1974, a Pan Am Boeing 707 on a night ILS approach to Pago Pago airport crashed on short final to runway 05 after experiencing heavy rain and windshear. 97 people lost their lives. The investigation stated: "The probable cause of the accident was the flight crew's late recognition, and failure to correct in a timely manner, an excessive descent rate which developed as a result of the aircraft's penetration through destabilizing wind changes. The winds consisted of horizontal and vertical components produced by a heavy rainstorm and influenced by uneven terrain close to the aircraft's approach path. The captain's recognition was hampered by restricted visibility, the illusory effects of a "black hole" approach, inadequate monitoring of flight instruments, and the failure of the crew to call out descent rate during the last 15 seconds of flight."

In February 1982, I was flying an Air Nauru Boeing 737-200 from Tarawa in the then Gilbert Islands (now Kiribati), to Pago Pago (NSTU) and thence to Apia, Western Samoa. Bad weather at Apia influenced our decision to overnight at Pago Pago. The following day we departed for Faleolo Airport, Apia, 80 miles away. Pago runway 05 was in use with a terrain requirement to turn right immediately after takeoff to a track out to sea of 087 degrees. Rain and low cloud were present for the departure.

Shortly after takeoff just as the landing gear had retracted there was a Hydraulic System A failure. That would affect landing gear and flap operation. We decided to hold at CELIM holding fix ten miles from the airport on the 087 radial from Pago VOR while we sorted out the problem. In 1982, CELIM was not in existence but there was a similar holding pattern on the 10 DME arc about ten miles to the NE. I have used CELIM in this story as an illustration only.

Hydraulic System A failure meant the landing gear had to be lowered manually and could not be retracted. It also meant that for landing the flaps had to be extended electrically to the Flap 15 position which took up to two minutes. Landing flap configuration as per Quick Reference Handbook (QRH) was Flap 15. Electric operation of the flaps was very slow which is why normal landing flap of Flaps 40 in the 737-200 is not recommended unless a serious emergency as they could not be retracted quickly in event of a go-around. A Non-Normal ILS landing was conducted in heavy rain.

Spare hydraulic pumps were sent from Apia and our engineer worked well into the night to change the A System hydraulic pumps. At the direction of our company we then departed in the early hours of the morning from Pago Pago direct to Tarawa. Because it was after hours, there was no ATC so we contacted Nandi on HF with depature details. The weather had worsened overnight with a strong crosswind component of 35 knots from the left for runway 05. While we expected some turbulnce from the nearby terrain with the highest ground being 1999 ft, we were caught by surprise at what happened next.

We had just turned right after lift-off to track 087 and started flaps retracting at 800 feet. Suddenly the rate of climb stopped and the aircraft began to descend despite the nose up attitude of 15 degrees, climb power selected and IAS 210 knots clean. The night was dark and we were in low cloud but very little turbulence. With the aircraft not gaining height, it.became clear we were caught in a very strong downdraught from the hills on the island behind us. We were about about four miles out to sea before we flew out of the downdraught and were able to resume a normal climb profile. If we had been on one engine the situation would have been dire especially as we were in IMC at night and unable to see he ocean ahead.

Some months later we heard that a Cherokee Six had disappeared at night after takeoff from Pago runway 05 in weather conditions similar to our own. The pilot had planned a long range flight to Tarawa and was overweight with extra fuel. Local aviation staff at Pago were well aware of the dangers of windshear and severe downdraughts when surface winds were 40 knots or more from the direction of nearby mountainous terrain. The pilot of the Cherokee Six was warned about this but replied he was already behind schedule and intended to go regardless of weather conditions. A foolish and fatal decision as it turned out.

The current Jepps aerodrome chart has a note that sea spray from surf and blow holes may drift across runway 05-23 under rough sea conditions. I don't know about present day but in 1982 there was no official warning of severe downdraughts after takeoff in strong winds. That was left to local knowledge..