Thank you for reading my writing.
I found out that C172S, C172P model POH doesn't have normal landing distance & soft field landing distance chart or table. It has only short field landing distance.
Does anybody know the reason?
Thanks.
1 Answer
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Typically light GA aircraft do not list normal landing distances or soft field distances in AFMs. Looking at the POH from a 172S
Look at Note 3, which refers to typical soft field conditions. It indicates that a 45% increase in the short field figures is representative of soft field landing distances.
As a “normal” landing distances vary depending on how aggressive one applies stopping techniques on the ground this distance is going to vary depending on how the pilot flies the approach and landing. Unless a specific procedure is described for this, as in the case for short field operations, there’s no way to draw up definitive performance tables for this. In addition, the critical value here is if the pilot has enough runway available to fly the approach and stop the airplane in the minimum distance required. If in doubt as to how much runway one will need during landing, the pilot should plan on using a short field procedure and use the published tables accordingly.
For general operations, I find an approximate 30% increase in the figures listed in these tables will provide a good margain for error and offer a conservative margain for landing figures.
Example: grass field, 4120 ft ASL, local altimeter setting of 29.83” Hg, 82° F (28°C), still air.
Pressure altitude is 4210 ft.
Using an E6B, the density altitude is 6,500 ft
Select 7000 ft from the table, 10°C column.
This gives a 730 ft landing roll from the table and 1585 ft distance to clear 50ft obstacle.
Increasing the ground roll figure by 45% for soft field gives 1059 ft ground roll and (1585-730) + 1059 = 1914 ft to clear 50 ft obstacle.
Increase by 30% for safety margin gives 1376 ft ground roll and 2488ft to clear 50ft obstacle.
answered Oct 25, 2018 at 5:24
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$\begingroup$ But older airplane POHs have normal landing distance chart or table. I guess I need normal landing distance chart more than short field landing chart. Do you know why manufacturer stop publishing normal landing distance chart? $\endgroup$– 이준세Oct 25, 2018 at 5:31
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$\begingroup$ Which airplane specifically has a normal landing distances published? $\endgroup$ Oct 25, 2018 at 5:45
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$\begingroup$ @이준세 Because if you are concerned about the length of the field, you should be using the short-field technique. Also, don't land at a field you can't take-off from, the take-off distance is larger than the landing distance, so if you want a "normal landing distance" yard-stick, use the take-off distance chart. $\endgroup$ Oct 25, 2018 at 13:31
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$\begingroup$ @CarloFelicione - used to be very common. Here is an example of a normal landing distance chart in a 1972 Cessna 172 (see page 6-5 at this link).joshwakefield.com/N3937Q/1972_C-172_Owners_Manual.pdf $\endgroup$– 757togaOct 25, 2018 at 16:52
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$\begingroup$ Oh yes, the old manuals written in the days when many companies are not held legally liable for omissions like that. No specification given for braking or stopping, etc. As such the data is virtually useless. $\endgroup$ Oct 25, 2018 at 17:25