Takeoff Performance Estimator
AirSmith, LLC

Frequently Asked Questions

1.       1. Why does the application include a prompt asking whether an aircraft’s Pilot Operating Handbook uses tables (rather than graphs)?

Currently, Cessna uses tables to predict takeoff performance. These are tables of values at different density altitudes and weights. To these values, the pilot applies factors to account for wind. 

The algorithm applies a different calculation for the table values than those applied to performance graphs.  Further, when tables are used in the application, the user interface creates fields in which you enter the wind factors. The value to a pilot is that it will not be necessary to add or subtract distance percentages when the winds change at the last minute.

2.       2. Why is there an application keyboard?

The application keyboard presents you with very large keys.  Ergonomically, the larger the keys, the easier it will be to enter or revise data.  This allows a pilot to quickly and conveniently evaluate any last minute changes in the prevailing conditions.

3.       3. Why is there no negative sign (-) on the keyboard?

The only place where a negative number needs to be entered using the application keyboard is in the temperature field. Since the system uses the Centigrade scale, zero degrees is 32 degrees Fahrenheit.   Limiting the system to temperatures at or above freezing is a reasonable safety factor in the application.  If a takeoff is contemplated under sub-freezing temperatures, using 0 degrees Centigrade can act as a safety factor.  

Under any circumstance where maximum performance is required for safety of flight, the Pilot Operating Handbook should be used.

4.       4. Can I display the aircraft type in the Takeoff Summary?

Yes. When you create an aircraft, enter the Aircraft Type (C-172N, C-182Q, etc.) in the Tail Number field and the Tail Number in the Aircraft Type field. The Library Screen will show the data in reverse order and the Takeoff Summary will display the Aircraft Type

5.       5. What is the reason for the Lowest Charted Distance?

The lowest charted distance field is an additional safety factor in the application.  Under unusual circumstances, including very light weights with negative pressure altitudes and cold conditions, the distance required result can be very short. This field prevents the system from returning a value less that any value in the Pilot Operating Handbook. 

A prudent pilot may also use this field to build in an additional safety factor.  For example, you may set a personal minimum of having no runway no-shorter-than 1,000 feet. You could enter the number you choose into this field, and the application would never return a distance-required result less than 1,000 feet.

6.       6. What is “wing loading,” where do I find it, and why do I have to enter it, when prompted by the application?

Wing loading is a term that refers to the number of pounds that need to be carried by each square foot of wing area at gross weight in non-maneuvering flight. Wing loading information is generally found on the “Performance Specifications” page of the Pilot Operating Handbook, or within the “General” section.  Occasionally the Pilot Operating Handbook provides the wing area only. In this case, the wing loading must be computed by dividing the gross weight by the wing area.

This value needs to be entered into the application, along with the wing span to yield the “aspect ratio” of the lifting surface. This ratio is used by the application to perform some high-density altitude calculations.

7.       7. If I change aircraft at the last minute, why should I review the previously-entered takeoff data?

Good practice calls for the takeoff data to be reviewed if an aircraft needs to be substituted.  It is reasonable to anticipate a situation where a pilot will plan a departure at or near gross weight, and find the intended aircraft unavailable for maintenance reasons. If a pilot switches to another aircraft that has a lower gross weight limitation, the originally entered takeoff weight could exceed the gross weight of the substituted aircraft. There are other performance considerations, as well, that need to be reviewed.

8.       8. How do I determine runway gradient?

Runway gradient is the slope of the runway. It is often expressed as a percentage and represents the difference between the elevation at one end of the runway and the elevation at the other end, divided by the length of the runway. If there is a 50 foot difference between one end of a 5,000 foot runway and the other end, the gradient is 1% (50/5000). The gradient is published in the Airport/Facilities Directory under RWY.  If missing, the gradient is negligible. Only the positive gradient is published. An entry that looks like “1.0% N” means the gradient is 1% when landing to the north.

Because there is no fixed decimal point in this field, you may use conventional rounding rules. For example, use “0” for any gradient between 0% and 0.5% and 1% for gradients between 0.6% and 1.0% and so on.

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