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Landing distances in POH

Im looking in the POH for the appropriate landing distance.
The max take off weight of the aircraft is stated elsewhere at 3050 lbs so why are we given reference landing distances for an impossible weight?
Strangely for the required take off distance there are two tables, each for different weights and therefore it’s possible to interpolate. Nothing similar for landing distances.

~800m for a single engine light aircraft approaching at 78kts seems like rather a lot.

Am I missing something?

Marsen wrote:

The max take off weight of the aircraft is stated elsewhere at 3050 lbs so why are we given reference landing distances for an impossible weight?

A good question indeed. I guess certification standards. I assume the rationale is that you might takeoff at 3150lbs, and therefore the situation might arise where you have to land a few minutes later, and thus, you would need to know what the landing distances would be in that case.

Marsen wrote:

Strangely for the required take off distance there are two tables, each for different weights and therefore it’s possible to interpolate. Nothing similar for landing distances.

A good question, too…
Marsen wrote:

~800m for a single engine light aircraft approaching at 78kts seems like rather a lot.

Well, remember this is landing distance, not landing roll. So it includes the glide over the famous 50 foot obstacle. If you check other fast four seat touring singles, you will find very similar values.

But keep in mind that in normal situations, your weight will be lower, and therefore your approach speed will also be lower.

Plus most short runways don’t have any obstacles (otherwise they would be almost impossible, i.e. bush runways), so in case of short runway, one will usually cross the threshold at a much lower height then 50 feet. Often just 3-5 feet. And in practice, the final approach speed will also be abandoned before reaching the threshold.

As a final note, your landing roll distances will hardly every be limiting in the underpowered and overweight SR20. As opposed to the SR22, it is takeoff roll-critical, not landing roll critical.

Mainz (EDFZ), Germany

Marsen wrote:

The max take off weight of the aircraft is stated elsewhere at 3050 lbs so why are we given reference landing distances for an impossible weight?

I wouldn’t exclude a typo in the POH.

boscomantico wrote:

Well, remember this is landing distance, not landing roll. So it includes the glide over the famous 50 foot obstacle.

Which at a 3° slope, is 290m by itself.

ELLX

lionel wrote:

Which at a 3° slope, is 290m by itself.

Only applicable for those who are flying ILS CAT3B and CAT3C mortals like us stop 3deg slopes at 200ft !
Also, I hope everyone cut throttle over 50ft threshold, with flaps and fly less than Vbg
Then they will can show less than 1:10 glides, so more than 8deg slope

Ideally, 1:4 (25deg slope) makes me happy !
That makes +200ft for 50ft threshold

Last Edited by Ibra at 08 Sep 14:25
ESSEX, United Kingdom

Actually, that’s interesting. What are the assumptions of pilot behaviour at threshold/50ft for the landing distance in the POH? That (s)he follows a 3° slope? Cuts power and maintains speed at Vref?

In the above POH, the difference between ground roll and landing distance at SL 0°C is a whopping 1748ft, that is 530m. That must include some distance floating to bleed off airspeed after the flare…

ELLX

lionel wrote:

What are the assumptions of pilot behaviour at threshold/50ft for the landing distance in the POH?

Ibra wrote:

Ideally, 1:4 (25deg slope) makes me happy !

25% slope is 14.5°.

25° is 42%, approx 1:2.5

Last Edited by lionel at 08 Sep 16:33
ELLX

What is the legal requirement to obey landing distances for non-commercial operations?

lionel wrote:

25% slope is 14.5°.

Sorry a typo 15deg (25deg is 46% slope)

Marsen wrote:

What is the legal requirement to obey landing distances for non-commercial operations?

UK CAA used to slap any book number with 1.41 something any time legal commercial operation is heard and extra factor
For non-commercial everything is left to pilot to decided but there is a POH and guidance for safety factors

Last Edited by Ibra at 08 Sep 16:35
ESSEX, United Kingdom

What is the legal requirement to obey landing distances for non-commercial operations?

There can‘t be anything like that, because the conditions underlying these tables/numbers (i.e. an exactly 50-feet high obstacle, right at the threshold) never exist in practice. In business speak, one would say it‘s a „KPI“ only…

Mainz (EDFZ), Germany
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