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Old 8th Apr 2006, 11:42
  #25 (permalink)  
john_tullamarine
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Several observations, if I may ..

(a) civil aircraft routinely are certificated to the normal approach speed (generally a minimum of 1.3Vso). As an aside, Chuck's tales in the previous post in respect of PNG are relevant to special operations but not for normal standard ops ... as far as I am aware, most of the cited exciting style of operations would have been conducted to the old Developmental Operations ANO standards .. I can't even remember what the number was ... it's just so long since I looked at those.

The military certification folk sometimes go for the serious STOL operation but accept that, in the event of an engine failure or other significantly serious mishap it is acceptable for a risk of peril to exist ... This is not acceptable for civil operations to the normal Regulatory standards.

On the other hand, the usually seen club practice of approaching at a speed very much in excess of the book figure is not to be recommended for operations into critically short (meaning that the available distance approximates that required for the operation) strips ... the aim is to approach at the scheduled target speed, in the scheduled configuration, get onto the ground following a minimalist flare distance, and get onto the brakes .. hard.

Consider whether the OEM might have set out to get the best data reasonably practical .. helps to sell the aircraft .. the club or line pilot is unlikely to come up with a better, yet still reasonably safe, procedure than that scheduled by the OEM.

The advantage of flying book speed is that the book distance bears some relationship to what you might expect to see. If you approach at a higher speed then, unless you have done the homework (not hard at all but most would not have the background) to generate revised P-charts for the non-standard approach speed, you are in no-man's land and might find that the far end fence comes up much quicker than you might have hoped for ...

(b) aiming to land on the strip end invites an undershoot mishap .. in the event that your sums were wrong, it is probably better to roll off the far end (or into the fence) at slow speed .. rather than hit a tree (or the fence) on the approach at POH approach speed.

In any case the manual data is based on the normal approach screen height so you have the basis for a normal approach and touchdown point. Consider where you want to have what level of risk when you consider doing a home-made approach and landing .. also how you might explain your actions either/both in court or to the insurance company.

(c) other things being equal, prefer uphill, into wind

(d) the old DCA Civil Mk II AFM format P-charts (? long time since I have looked at or drafted up one of those) gave distances which were generally reasonable but with not too much fat in their generation (when one considered the unfactored values). The ANO (CAO) distance factors were there to provide a little in the way of fat for the average skill level pilot (believe me .. the average club or line pilot will .. no way ... reproduce the OEM TP's performance landing data - I have had a few frights at the hands of such very focussed gentlemen).

If you are using the GAMA US POH manuals, make sure you know what factors, if any, are included in the data .. and adjust your calculations appropriately, as necessary.

(e) if you are the typical club pilot who has generally operated out of non-critical length strips (BK, MB, etc. come to mind), then be prepared for a whole new ballgame if you contemplate critical length ALA type operations. Suggest you get a good grounding and check out by folk who know what they are doing ... and I suggest that is not the typical flying instructor ... rather the experienced ag (especially) or glider tug pilot (one who has a LOT of paddock retrieve experience) ... and preferably one who holds a relevant instructor rating so that the niceties are observed.

For instance, in a previous towing life, I was required to observe a number of paddock retrieves in the back seat and then do a semi-formal period of instruction and check out by a very experienced ag pilot (took around 2-3 hours as I recall). I learned a LOT which I would never have been exposed to otherwise. This suggestion is not one which you should consider lightly. He who embarks on paddock operations (or very short country strip operations) is foolish not to seek specialist instruction in the hazards .. of which there are more than a few.

(f) regarding "aerodynamic breaking" (and the typo was intentional) I would invite anyone to present verifiable test data which even suggests that that sort of technique is better than a good bootful of braking ... (looking at the serious short strip requirement)

(g) .. and the main thing is .. be conservative ... if you are not comfortable with the approach and landing at any stage, give it away and either try again or divert. Most of us who haven't bent a bird have done both without any second thought as to the possible inconvenience.

The only people who have to push their luck a bit are the military (when operationally necessary) or civil when the alternative presents a higher potential hazard .. and, if the planning and conduct of the operation has been done in a half competent manner, that ought not to occur other than very infrequently.
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