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5 Answers

Exceeding performance charts

Asked by: 5671 views FAA Regulations, General Aviation, Private Pilot, Weather

Looking in the Cessna 172S POH I see the performance charts give temperature ranges from 0 to 40 degrees C. If temperature outside exceeds 40C then does it become illegal to takeoff? I would imagine it would be illegal since you are now no longer able to abide by 91.103 by knowing takeoff/landing performance.. Thanks!

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5 Answers



  1. John D Collins on Jun 21, 2015

    Since there isn’t an OAT limitation in section 2 of the POH, I would simply extrapolate the data using the existing performance charts and add a 50% buffer. But you are not going to get me in any airplane without an air conditioner at 40 C, much less a higher temperature.

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  2. Mark Kolber on Jun 21, 2015

    It’s not illegal, As John indicates, the performance tables are guides, not limitations.

    Extrapolation can potentially be dangerous. As density altitude goes up, the hit on performance is not linear; the variation increases above a certain density altitude.

    I think a better choice is to remain on the charts if you can. Understand that the the performance tables are ultimately giving you density altitude information, which is the real measure of performance.

    So for example, if I were taking off at sea level when it was 50°C (I’m really not too interested in leaving my air-conditioned home in 122°F temperature), I’d feel much more comfortable using another portion of the chart that also gave me numbers for approximately 4,000′ density altitude, like the 1,000’/40°C box.

    There may indeed be times that we really have to get off the chart. In that case, in the absence of actual experience, we will extrapolate or use rules of thumb to get a guideline number while understanding that we are essentially test pilots at that point (although in certain parts of the country, the “test piloting” has been done for decades and we are just learning from others’ experience).

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  3. Kris Kortokrax on Jun 23, 2015

    Looking at the POH for a Malibu, in the Limitations section, it contains the following statement:

    “Refer to Section 5 (Performance) for maximum weight as limited by performance.”

    In the Performance section, it contains the following statement:

    “Performance information derived by extrapolation beyond the limits shown on the charts should not be used for flight planning purposes.”

    To me, this means that a pilot is not allowed to takeoff if the temperature exceeds that which is depicted in the performance charts.

    Further, if one were to extrapolate data for a temperature higher than depicted and subsequently have an accident or incident, it could create problems when dealing with NTSB or FAA.

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  4. Mark Kolber on Jun 24, 2015

    I’ve seen the “don’t extrapolate” language in a number of different manuals.

    But I don’t see the “should not” as a prohibition against taking off (any more than”slips with flaps not recommended” is a limitation because the placard is required).

    If the “don’t extrapolate” language were a limitation, there are a lot of flights in the Rockies, by very capable mountain pilots, that have flaunted the rules for decades.

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  5. Kris Kortokrax on Jun 26, 2015

    I would say that the language concerning the need to determine the maximum weight is a limitation. It directs the pilot to use the performance info to determine the maximum weight.

    As I said earlier, if there were a mishap, I would think that the FAA might ask how the maximum weight was determined. As you said, the extrapolation is not linear.

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