Pitot tube

[FMild]

I was walking around my aircraft with another Cessna owner, and he commented that it looked like my pitot tube was angled a bit. It does appear that it is angled 15-20 degrees away from the axis of the aircraft, although there is no skin wrinkling or any obvious bends or twists in it. Is this normal, or is it something I should have replaced? It makes me curious because it seems that in normal flight I'm only getting about 165 mph (140 KIAS) instead of the 160 KIAS I've been told is the normal cruise speed, which if the tube is not properly aligned would explain the difference. Any thoughts?

[tropical]

Originally Posted by FMild

I was walking around my aircraft with another Cessna owner, and he commented that it looked like my pitot tube was angled a bit. It does appear that it is angled 15-20 degrees away from the axis of the aircraft, although there is no skin wrinkling or any obvious bends or twists in it. Is this normal, or is it something I should have replaced? It makes me curious because it seems that in normal flight I'm only getting about 165 mph (140 KIAS) instead of the 160 KIAS I've been told is the normal cruise speed, which if the tube is not properly aligned would explain the difference. Any thoughts?

IAS is "indicated airspeed". The Skymaster (NA) at 6000' Standard day will get about 160Kts TAS (true airspeed).

A very simple formula is TAS = IAS + (2% IAS per 1000 ft altitude).

So at 5,000 ft if you are indicating 165mph, your TAS is 181mph, converted to Kts is 156kts.

[edasmus]

Your IAS of about 140 knots or 165 mph is in line with what my 73G model indicates. My true airspeed is usually about 180-185 mph or 155-160 knots. It does not sound as if your indicated airspeed is obviously wrong but I cannot speak for the angle you mention as the 1973 models have a completely different pitot tube arrangement altogether than the earlier models.

Ed