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#11
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Airspeed Indicator Accuracy Tolerance
Very helpful. Thanks. -Sami
Bob Gardner wrote: Don't know if this helps. It is important to remember that the radial blue line is based on sea level, on a standard day, at max gross weight. Change any of the parameters and the blue line is inaccurate. Bob Gardner § 23.1323 Airspeed indicating system. (a) Each airspeed indicating instrument must be calibrated to indicate true airspeed (at sea level with a standard atmosphere) with a minimum practicable instrument calibration error when the corresponding pitot and static pressures are applied. (b) Each airspeed system must be calibrated in flight to determine the system error. The system error, including position error, but excluding the airspeed indicator instrument calibration error, may not exceed three percent of the calibrated airspeed or five knots, whichever is greater, throughout the following speed ranges: (1) 1.3 VS1 to VMO/MMO or VNE, whichever is appropriate with flaps retracted. (2) 1.3 VS1 to VFE with flaps extended. (c) The design and installation of each airspeed indicating system must provide positive drainage of moisture from the pitot static plumbing. (d) If certification for instrument flight rules or flight in icing conditions is requested, each airspeed system must have a heated pitot tube or an equivalent means of preventing malfunction due to icing. (e) In addition, for commuter category airplanes, the airspeed indicating system must be calibrated to determine the system error during the accelerate/takeoff ground run. The ground run calibration must be obtained between 0.8 of the minimum value of V1, and 1.2 times the maximum value of V1 considering the approved ranges of altitude and weight. The ground run calibration must be determined assuming an engine failure at the minimum value of V1. (f) For commuter category airplanes, where duplicate airspeed indicators are required, their respective pitot tubes must be far enough apart to avoid damage to both tubes in a collision with a bird. [Amdt. 23-20, 42 FR 36968, July 18, 1977, as amended by Amdt. 23-34, 52 FR 1834, Jan. 15, 1987; 52 FR 34745, Sept. 14, 1987; Amdt. 23-42, 56 FR 354, Jan. 3, 1991; Amdt. 23-49, 61 FR 5168, Feb. 9, 1996] "O. Sami Saydjari" wrote in message ... Scott Skylane wrote: O. Sami Saydjari wrote: /snip/Isn't there a way to judge true accuracy of speed indicators (just as there is for altimeters)? Should I be satisfied with my mechanic's answer and move on? -Sami N5554G, Cessna 421C Sami, There certainly are maintenance actions you can take to ensure your airspeed indications are as accurate as possible. Both airspeed indicators can be sent to an instrument shop for check/overhaul. Arg. Sounds like a hard way of finding out. Any competent mechanic can check your pitot and static systems for leaks and /or abnormalities. Just did a Pitot Static check. Once these are all done, your system will be as accurate as originally designed. Keep in mind that *some* aircraft are designed so that one side is accurate at lower speeds, and the other accurate at higher speeds, but I doubt this is the case with a twin Cessna. The above info does not infer whether the expense incurred would be worth the outcome, that is a decision only you can make. P.S. When did you sell your Turbo Arrow I have not sold my beautiful Arrow yet. and get that bottomless money pit? I got half-share in the C421 in mid-November. So, the good news is that it is only a half-bottomless money pit Happy Flying! Scott Skylane |
#12
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Airspeed Indicator Accuracy Tolerance
Actually, I can't believe that this would your worst problem!! Bill Hale
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