Morning all, Forgive if this has already been covered in the forum-but I have a question. Let's say the scenario is this-I am flying in a cherokee 180 into a strip of which has no RDS but has a measured leingth of 460m. The performance charts for my aircraft I have are at max weight, no other weight, so no interpolation for a lighter weight ie all calcs must be at max weight.
Now-we do the chart and see that we need more like 700m (including 50ft clearance), so no go. However...at one end of the strip it is essentially flat for miles, so can we use this as our 'clearway?'

What it boils down to, is that when casa says in 20.7.4 '...achieve take-off safety speed at a height of 50 feet above the take-off surface...' is that 50ft above the runway allowed to be downrange (400m on from the end of the runway at 50ft) or has to be immediately above the runway (50ft over the upwind threshold).

Short answer is "no, you can't be innovative with clearway".

However...at one end of the strip it is essentially flat for miles, so can we use this as our 'clearway?'

Several points.

(a) clearway is only relevant for takeoff

(b) there is an airports standards limit on the amount of clearway permitted so unlimited is not appropriate. Further, for declared data on most country strips, the clearway is quite modest and doesn't present a problem ref (c) for lighties

(c) the problem with clearway is that you still need to make sure that you are off the ground somewhat prior to the end of the runway proper .. for fairly obvious reasons.

Hence use of clearway performance calculations is restricted to heavy aircraft which have both takeoff distance required (TODR) and takeoff run required (TORR) data in the AFM (think POH).. TODR is much the same as TOD calculations for light aircraft and addresses getting to the screen height (50ft for lighties, 35ft for heavies). TORR covers getting off the ground prior to the end of the runway proper. The usual arrangement is that TORR gives you a liftoff position such that you will have no less than one half the air distance to screen over the runway proper. (Older UK standards had this as one third but you won't see many aircraft with this older standard as time goes on).

So, sorry, it's either per the CAAP or just use the ERSA declared TOD for lighties.

Sidenote - with max weight only charts, do be careful. The landing distance (for the constant max weight approach speed) will increase at lower weights due to an increased float during the flare. The only way to counter this is to adjust the approach speed down to suit the weight - if you do this, be careful of PEC errors when figuring the reduction in speed.

Those of us with a performance engineering background probably would do our own sums to see if the lighter weight might be OK but that is not appropriate for the line pilot's use.

Thanks for the prompt reply.

So in essence, if my runway is 460m and the distance between the gable markers is 500, and my T/O distance required to 50ft is 720m using the max weight graph so it's a no go (ground roll is 335m so we will get airborne before the piano keys). One end of the runway is clear of all obstacles as per the caap (45m 2.5% up)-it goes over water. That's where my question lies, is that over water clearway for chart purposes?

I guess we all thought about this sort of thing as students ..

(a) CAO 20.7.4 definitions - take-off distance available means the distance specified by CASA as being the effective operational length available for use by aircraft for take‑off at certified or registered aerodromes or the distance available for take-off on an aircraft landing area.

(b) CAAP - you can't really pick and choose which bits you like and discard that which you don't like

(c) “clearway” means an area in which there are no obstacles penetrating a slope of 2.5% rising from the end of the runway over a width of 45m; That's nice but one needs, also, to consider the following bits ...

(d) “runway” means that portion of the landing area which is intended to be used for the landing or take-off of aeroplanes;

(e) 5.2 Runway Length. For other than agricultural operations by day, a runway length equal to or greater than that specified in the aeroplane's flight manual or approved performance charts or certificate of airworthiness, for the prevailing conditions is required (increasing the length by an additional 15% is recommended when unfactored data is used). Now do have a look at the various graphics in the CAAP ..

(f) I see no useful reference to clearway for light aircraft in the CAAP nor, I suggest, will you find any in your POH. Indeed, in the CAAP, there are only two references to clearway; viz. the definition and for ag ops takeoffs.

So, I suggest, no .. the water is irrelevant. Clearway is heavy iron stuff .. not lighties.

Also,

(a) what provision are you proposing to make for itinerant obstructions such as yacht masts ?

(b) are you sure that your story might hold up in Court following a mishap ? .. regardless of whether the ALA had anything to do with the mishap ?