Takeoff Planning - What am I missing?

[YesTAM]

Without wishing to get involved in P**ssing contests about flaps etc. I have a real problem I need to solve.

I'm planning a trip to Arkaroola, been there before (its a great place) it has 650m strip of gravely sort of soft shale draped over a low hill - it rises about 20 feet in the centre. There are no obstacles at either end within at least a mile or so.

Been there before and took a C172, no problems. This time however I'm planning to take an Arrow, about 120 KIAS cruise, autopilot and so on, just a little more comfortable.

Trouble is, I'm not sure if takeoff perfomance is problematic or not, and I want to discover what I'm missing.

I've assumed 20deg C. Assuming MTOW, and before allowing for slope and surface there is no way I can get back out as the takeoff ground roll alone at MTOW Flaps 0 deg. is 2000" (650m = approx 2100ft).

Now there are charts for flaps 25 deg and the ground roll is about 1250 ft. In theory therefore, and knowing the strip, I can get off with flaps 25.

Now before everyone starts screaming "read the POH", I have read the POH.

I have issues here:

1. I haven't practiced a short flaps 25 degree takeoff in an Arrow at MTOW - yet, and thats easily remedied.

2. I'm not sure what to allow for the gravel surface. I do know from the tracks etc, that if its wet it gets "mushy" and probably I won't be going.

3. I'm not sure what to allow for slope because I know that the "down" component doesn't quite compensate for the "Up" component

4. I know the old saw about how the charts are made with reference to a new aircraft, engine, prop and test pilot, but what degradation should I allow? Both for the aircraft and myself?

5. I've looked at weights, fuel loads etc, but there would only be 50-75 kilos between full fuel and a "trimmed" amount that severely trims my options after takeoff (especially if it is windy) and would only change ground roll distances by about 250 feet. In other words, if thats all thats in it, I might as well plan for MTOW (I'll be just under that with two of us, say 40kg, bags, cameras, tiedowns, oil and the usual junk that accumulates).

6. And no, I'm not taking off on the road instead. It would void the insurance.

So what am I missing? It appears from the charts that I can get off, but I certainly can't make a 50 foot obstacle, not that I need to at Arkaroola.

signed (vaguely uncomfortable) YesTAM.

[Capt Claret]

YesTAM,

It's been many years since I've flown an Arrow or used GA aircraft P-Charts. I thought the PA-28*s I flew years ago had P-Charts for the first stage of flap, which I thought was less than 25 degrees. Again, as best I can recall, gravel was considered as sealed, it was only grass which had onerous factors.

Or is my memory just fading with old age?

[glekichi]

Aren't P charts usually to a 50ft screen height anyway, rather than ground roll?

[john_tullamarine]

Some thoughts .. and it's a long time since I drew up any of the old style P-charts so my comments may contain the odd little error ..

(a) distances are to 50 ft screen and factored .. if you have an old chart the factor should be listed or can be inferred from the old ANO/CAO 101.22 if you can get a copy .. I have one somewhere in the archives and I am pretty sure that djpil will have one tucked away ... Very few charts around which would only give you the ground roll.

(b) gravel normally attracted an additional 15 percent factor for the privilege ..

(c) I haven't practiced a short flaps 25 degree takeoff .. the P-charts were based on normal sort of flying .. ie fly to the nominated rotate speed and do so .. or pick a suitable margin a little below the nominated Vtoss to rotate .. nothing special required. However, if the surface is very soft, I suggest that all bets are off for these charts ...

(d) I'm not sure what to allow for slope .. as there is no requirement for an RTO, why not just do the calcs for max up slope, max down slope and level ... and take the most conservative answer ? In general you won't have enough information to do anything fancier than this ..

(e) charts are made with reference to a new aircraft, engine, prop and test pilot .. often the charts were based on a quick series of tests with an old bird and very average pilot or a couple of points pinched out of the US POH data ... in general, there is enough fat in the P charts not to need to worry too much about the bird and driver (DCA, and its variants, went to reasonable pains to put in a reasonable amount of fat while avoiding so much that people would not take the charts seriously) .. but factor in whatever you feel is a reasonable number .. it all comes down to a bit more for conservatism, mum and the kids .. etc .. and, if you are paying the cost, it is up to you to determine how fat a margin you might wish to have ..

At the end of the day, the croppy's techique of doing a couple of trial runs, starting empty and working up towards the desired TOW .. makes a lot of sense if you have a twitchy feeling that you might be pushing your luck at bit ...

And, when it comes to the time to make the final decision, if you aren't pretty happy that all is well .. then the decision has been made for you ...

Long time since I have looked at an Arrow .. can you scan and post the charts somewhere and we can offer some comments structured to the particulars ... ?

[Chimbu chuckles]

Yestam I have never flown an arrow and dont know the strip so can only give generic advice.

If what you have said about the flaps 25 TORR is correct you will be using about 60% of the TORA...that is enough buffer IF you are allowing for the slope. You said the strip is 20 foot higher in the middle...what is the slope either side?

If you know that assume your entire take off run is upslope...because it is going to be, near as damn it.

Just eye balling YOUR figuresit is 20 feet in 1000...2/100...2%...does your POH have figures for 2%?

If the surface is gravel you wont want to start your takeoff roll from a full power standing start but rather a running start started in your turn to line up...use as wide a turn circle as possible and feed the power is as you roll around..that gives a little more buffer because you start your takeoff at 5kts or so. Even widen the line up turn out as far as starting from one side of the runway and slowly regain the centerline will give you a few more kts head start. Maybe practice this during your flaps 25 practice pre trip?

It is nice for your prop too rather than small rocks pinging off the blades.

If there are no obstacles dont worry about TODR...get airborne and accelerate in a gentle climb cleaning up as you go.

[Chimbu chuckles]

JT it is highly likely yestam does not have the old DCA charts that gave factored TODR. The CASA mandated change to manufacturer POHs and ´amendment services`a few years ago removed them from reach for all but those of us blessed with owning aircraft from that era...I didnt throw mine away

[SCE to Aux]

Arkaroola is a great place and the owners are very much aviation people. Talk to Doug Sprigg at Arkaroola about the strip, you'll find his advice most helpfull. If you have any doubts about your aircraft, why not land at Balcanoona, it's a nice sealed strip only a short distance from Arkaroola. The people at the resort will happily meet you at Balcanoona and take you back when you're ready to go. I'd personally be quite happy to take an Arrow into Arkaroola, but you are the PIC so it's your call. Have fun, I love the place but I'm half a world away and jealous!

[QSK?]

Factoring Guidelines

YesTAM (and others who bemoan the passing of factored P-charts):

You might like to try this link to a UK CAA advisory publication on GA aircraft performance useful. Goto:

http://www.caa.co.uk/docs/33/SRG_GAD_WEB05SSL7.PDF

With the newer Australian P-charts that have no factoring, I use the factoring guidance in this publication to assist.

Hope this is helpful. You'll also note there is a recommendation for a 10% factor for a 2 degree slope.

[squawk6969]

Here it is




And its quite a downhill run, and I reckon the last 100m to 150m we did not use, but that was 2 POB some gear, and maybe 3/4 fuel or a bit less.

The video I have is quite impressive!

I think find a long runway, and test it a few times to get a feel, and if in doubt don't. I never want to be needing the last 100m of any runway! Unless its to take a walk along!

SQ

[Fhead]

yeah the arrow likes a nice long takeoff. but I think the you can get p-charts for run required and for distance (to 50ft) in the arrow manual.

[Plow King]

Gday YesTAM

Just me, but if I was in an Arrow I'd probably favour Balcanoona (mainly because I haven't been in there in a while), it's really not that much further for the pickup and might be worth the peace of mind. In the event you get any sort of reasonable westerly coming across that range to the west you'd need a couple of extra knots on final; if the prevailing wind has any sort of southerly component it could require landing down-slope. And from what I remember there, on departure a couple of knots on the tail is a better option than taking off to the north. I depends on the Arrow too; one in particular I remember, I would be nervous using 08/26 at PF, let alone Arkaroola

But as SCE said, Doug is the man, and you're the PIC; it's whatever you're comfortable with. Have a ball, I'm jealous too!

Plowy

[john_tullamarine]

.. for a slab or two, I'm sure that djpil or I could run up the odd old style P-chart .. the formulae are pretty straight forward if one uses the older protocols which Ronnie et al developed ... if using JCF's later paper, it gets a lot fancier and more complex ... all good, clean fun it was ...

[desmotronic]

Yestam,
You dont seem to be missing anything except the wind component.

[Biggles_in_Oz]

What sort of Arrow ?
T-Tail or 'conventional' tail ?

The T-tail needs more takeoff distance due to a lack of prop-driven airflow over the elevators.

[gaunty]

YesTAM

As far as P charts are concerned listen to john_t all else is horsefeathers. And no they definitely were NOT derived from a Chuck Yeager performance anymore than the "factory" POH numbers were. The FAA requirements are for "average" everything. That is it must be able to be reproduced by the "average" pilot in an "average" aircraft.

If you can find a copy of the original P charts for the type they would be pretty conservative as the regulator was of the view that the manufacturer was gilding the lily somewhat.

Whatever decision you make, and it is yours absolutely and entirely, just make sure that it will stand on its own and the rational scrutiny of the legal process, not, I heard it on PPRuNe.

When I see the Dr say I wouldn't take a C172 out, scared myself in a Cutlass, M20J in and out and a C210 would eat it, you gotta wonder. Not doubting that the Dr had any one of those experiences but without some qualifying data it is, in and of itself, totally meaningless and certainly not something to make a decision on. Under the right conditions I could get a C421C in and out too the same way a C172 should not present any problems except under extreme conditions.

From a global perspective the manufacturers all designed their aircraft types to be competitive within their market segments, ergo if one can it is reasonably possible that the other will. Some do it better than others at the extreme ends of the envelope, but they will all do it more or less. Cessna better than most.

[YesTAM]

All commentary gratefully received. I can add a little more detail.

I have the old DCA P charts for the T tailed model (PA28RT), but they are of no direct use, as far as I can tell, because they calculate TODA. not takeoff ground roll.

I also compared takeoff roll and distance to 50 feet for the high and low tailed Arrows and the high tail actually has slightly better takeoff perfomance.

So anyway I'm back to the POH for the charts.

These show that at an arbitrary 20 C and a pressure altitude of 1000 ft (Arkaroola alt. is 800 ft) and at MTOW with flaps 25, the ground roll is 1200 ft. Ignoring wind, and adding 10% for slope and another 10% for surface, and another 10% for age and another 20% for general stupidity, this gives a ground roll of 1800 feet or 548 metres and its a 650 metre strip.

My little Sporty's takeoff calculator says 1700 feet. Considering that there are no obstacles it should be OK..

Found some photos, forgot how good the strip was - taken from the RHS of Doug Spriggs 207(?), can't wait to get back there, Arkaroola is a magic place.:

[185skywagon]

Obviously, a takeoff to the south would be also preferrable due lower terrain. This is dependant on wind of course.
Been in and out of there a few times in the 185 with a full load.
make sure your "t"'s are crossed etc, or remove all doubt and go to Balcanoona.

[squawk6969]

YesTAM

I hope you have a great trip, mind you I am puzzled as to what is out there that is so interesting, maybe its got something I should go see too.

And the Pic I posted above, where the heck did the post go asking for it?

The FTDK said I had a pic of the 600m strip up hill, so I posted it, and now its meaningless without his post. Just emailed the FTDK and guess what? He has not removed it.

What is going on here? Did you ask for it to be removed YesTAM?

Anyway have a nice trip.

SQ

[YesTAM]

Nope, don't know why its not there.

[BrokenConrod]

What's the attraction at Arkaroola?

BC