The Seat Position Sight Gauge on the ATR 72

The ATR 72-500 has its idiosyncrasies. In the cockpit is a “seat position sight gauge”, which are three small, coloured balls that allow a pilot to adjust his viewpoint to a position that ATR deems appropriate, allowing for a “correct view of instrument panels as well as runway environment”. The photo above shows the ATR 72 cockpit, with the sight gauge enlarged in the inset. If the first officer is to have his viewpoint right, he must adjust his seat height and position such that when looking at the three balls, the left white ball is obscured by the red centre ball.

Eye Level Indicator on the Q400

Interestingly, this gauge is not found in the Boeings, where the recommended method of adjusting the viewpoint is different. The ATR 72-500/600’s competitor, the Q400, however, has something similar, called the “eye level indicator”, as may be seen in the second photo. The Airbuses, not surprisingly, have a sight gauge similar to that found on the ATR.

Possibly one of the smartest first officers in India told me, after seeing me so diligently adjusting my P1 seat in an ATR 72-212A (500) to the correct viewpoint, that I was too high. Apparently, the seat position sight gauge does do its job well, but it isn’t something you’d want to level your eye with on an airplane like the ATR 72-500. Why? Visual perspective.

With the eyes adjusted, the view is good, and clean. But with the ATR 72, (and the Q400) one has to be very careful with the flare: the airplane’s fuselage is long and low, and a tail strike is easy. Another complication is the aircraft itself: having a constant speed propeller means that when you pull back on the power levers, the pitch angle of the propeller blades changes to “fine” (almost perpendicular to the direction of the airplane’s travel through the air), resulting in a significant increase in drag. If the flare is more than required, and the airplane balloons*, pulling back on the power levers is the last thing one would want to do, as the drag would make the aircraft drop to the runway like a stone!  So one would add power to keep the airplane up, and this will eat up more runway: Messy indeed. And for him, with the ATR recommended viewpoint, comes the tendency to flare more than required.

*[The term “balloon” refers to a landing airplane that rises slightly before touching down. Ballooning is typically caused by excessive airspeed or excessive back pressure being applied to the flight controls by the pilot during the landing flare]

So what he does is to sit lower than the recommended view point: low enough to make him actually look up to see outside. This works well for him, and few others who have settled for this more comfortable, though not recommended, seating technique. Anything that works!

What can go wrong just because of an improper flare?

On 9^th May, 2004, N438AT, an ATR 72-212, during the approach to landing, the captain stated to the first officer (flying), “you better keep that nose down or get some power up because you’re gonna balloon.”. After the airplane crossed the runway threshold, the captain stated, “power in a little bit, don’t pull the nose up, don’t pull the nose up.” The captain then stated, “you’re ballooning,”. The airplane touched down with a vertical load of 1.3G, bounced into the air, touched down a second time, then bounced into the air with a nose up of 9°, climbed to 37 feet, and touched down a third time with a vertical load of 5Gs. After a fourth touchdown, the badly damaged airplane came to a stop outside the runway.

On 17^th September, 2005, D-ANFH, an ATR 72-212A, Just prior to touchdown, the co-pilot pitched the aircraft nose up to an attitude of 6.5º. The aircraft landed hard on the runway and bounced; in the course of the initial touchdown, the lower rear fuselage struck the runway surface.

On 23^rd May 2006, G-BWDA, an ATR 72-202, towards the conclusion of a brilliant approach, the first officer closed the power levers at 10ft and flared the aircraft. The airplane touched down, bounced into the air, and the attempt to arrest the sinking of the aircraft to the ground, pulled back on the control column, striking the tail.

And yes, I have also heard some of my friends say, “Oh damn, I forgot to flare!”