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Short Field Landing Airspeed Conundrum

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Short Field Landing Airspeed Conundrum

Old 10th Jul 2017, 15:14
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Short Field Landing Airspeed Conundrum

The Short field Landing Conundrum.

The July 2017 revision of the CASA Flight Examiners Handbook requires the applicant demonstrate a short field landing for the following flight tests: RPL A, PPL A, CPL A, SEA Class.

Early post war standard operating procedures at flying schools included short field approach and landings that were based upon normal landing speeds for the type minus ten knots as an approximate figure. For example the Pilots Notes for Tiger Moth aircraft (RAAF Publication No. 416 dated February 1944) showed 58 knots for glide and engine assisted approaches. For Precautionary Approach and Landing the correct speed was 48 knots which was assumed at 250 feet. You were really hanging on the prop

Pilot’s Notes Chipmunk T10 (A.P. 4308A-P.N) recommended over the fence at 55-60 knots. The precautionary approach crossed the fence at 50 knots. Note the term Precautionary Approach is nowadays called Short Field landing.

Pilot’s Notes for Sea Fury (A.P. 4018A-P.N) displayed final approach speed at max landing weight as 125 knots and for a carrier deck landing the recommended speed is 90-92 knots with the caveat that it is necessary to pull the control column well back to effect a three-point touchdown. In current parlance that is around 1.1VS in the landing configuration.

In contrast the Cessna 172N POH recommends a normal airspeed on approach with flaps as desired (ie flaps up to Flaps 40) as between 55-65 knots. Published short field full flap landing approach is 59 knots until flare.

A major difference between a true short field or precautionary approach and landing and a normal landing (see RAAF Pilots Notes above) is with the precautionary landing there is more drag on approach, a lower approach speed and thus a shorter float and ground roll.

RAAF Pilot’s Notes do not include landing distance information whereas the Cessna POH includes a table based upon 59 knots at 50 feet. The airspeed is based on approximately 1.3Vs in the landing configuration. The landing distance and associated airspeed at 50 feet is a characteristic of American aircraft POH.

Having observed many flying school pre-flight briefings on so called “short landings” versus normal landings, the majority of instructors talk about lack of float in short field landings. That was correct in the old days where speeds for a short field or precautionary landing were roughly 10 knots slower than normal. Nowadays that doesn’t happen anymore, simply because current landing speeds in typical light aircraft POH are based upon 1.3VS. After all, for a true short field landing it is desirable to touch down with practically no float to enable a shorter landing roll. In a tricycle landing gear type which means the majority of today’s aircraft, it is unwise to force the aircraft on the landing surface while it still has flying speed where the danger is damaging the nose-wheel if it hits first. So a float is necessary to dissipate over the fence speed to actual safe touch down speed which should be at the point of stall.

Large transport aircraft have published approach speeds of approximately 1.3Vs in the landing configuration. These are not called short field landings. They are normal landings. Why then is the same principle not applied to the everyday landing in a typical Cessna, Piper or Beech light single that use 1.3Vs ie normal landing as against the use of the term “short field.

It could be argued it is reckless flying to approach deliberately below the POH published 1.3Vs figure. In days of yore and because of the exigencies of the Service, military aircraft could often be required to land in fields of unknown dimensions and unknown surface. A slower speed than normal would be therefore needed to ensure minimum ground roll. In fact, it was not long ago that CASA changed the title of short field landing to minimum ground roll landing. Now the Flight Examiners Handbook has discarded minimum ground roll and for some reason has gone back to short field. Some would argue this is a retrograde step.

Summary: Instructor training schools should ensure briefings on short field landings delete reference to alleged minimum float characteristics when approaching at 1.3Vs. The accent on short field landings should be on accurate touch down point and associated minimum ground roll. The approach speed for so called short field landing and normal landing is the same at 1.3Vs. There is no landing airspeed differentiation with larger aircraft between a limiting runway length and one with excess landing distance available. However in large aircraft the ground roll distance is highly dependent on stopping aids such as ground and flight spoilers, reverse thrust, and anti-skid devices.

A recent US Flyer magazine reader’s contribution about how to fly a short field landing will probably raise a few eyebrows among PPRuNe readers. Quote:
“Since the approach speed is likely only a few knots above stall, it is critical to fly accurately. MacNichol challenges her students to stay within 0 knots below and 1 knot above the target speed to enable the shortest landing possible while minimizing the risks.” Unquote.

And guess what? That’s exactly what we did on Tiger Moths, Wirraways and even venerable Austers in days of yore..
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Old 10th Jul 2017, 17:19
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Originally Posted by Centaurus View Post
The Short field Landing Conundrum.

And guess what? That’s exactly what we did on Tiger Moths, Wirraways and even venerable Austers in days of yore..
Agreed Centaurus.

Those having had the privilege and pleasure of flying the Auster J1N A with the de Havilland Gipsy Major , myself included, will need no further convincing.
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Old 11th Jul 2017, 00:58
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That endless dumbing down exercise, known as mindless risk control...

I count myself fortunate to have had a number of instructors over the years that have had the attitude, that it's better to face a slightly increased risk of bending something under controlled circumstances, than to face a completely unfamiliar situation when the poo goes through the prop for real. So practice forced landings, at least some of the time, went right to ground level on a farm road kept clear by arrangement (as I found out afterwards) and short field landings most definitely required an understanding and application of back of drag curve flying, with 1.1VS being the desired mark.
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Old 11th Jul 2017, 02:19
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Those having had the privilege and pleasure of flying the Auster J1N A with the de Havilland Gipsy Major
I have never considered flying an Auster to be a pleasure! The least favourite aeroplane in my log book.
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Old 11th Jul 2017, 03:56
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...Since the approach speed is likely only a few knots above stall...
Criky!.. makes me hair stand on end just thinking about it. In the 182 sized machines on a standard Oz summer day that sorta flying will bite one day - Heavy touch down or at worst a short final stall/spin.





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Old 11th Jul 2017, 04:13
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I have never considered flying an Auster to be a pleasure! The least favourite aeroplane in my log book.

Comments like this are why PPRuNe needs a like button!
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Old 11th Jul 2017, 05:46
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Follow the POH, no such thing as a short field landing. If the POH P charts say too short then the runway is too short.
The PA 28 P charts approach speeds vary with weight and are designed to achieve a short ground roll anyway.
Max weight is 65 kts and empty 49kts. So pick your landing weight and therefore approach speed to workout LDR for the conditions on the day.

If the P charts say cannot then cannot.

If in emergency then obviously all bets are off anyway and you do what you have to.

For simplicity of students a standard approach speed for all weights ( around 65 kts ) and a slow speed for short field performance ( maybe 55 kts ) when infact we should adjust the approach speed for all weights and conditions everyday anyway just like in a Jet.

KISS method.

Last edited by ACMS; 11th Jul 2017 at 05:59.
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Old 11th Jul 2017, 06:36
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I hope we all realise that stall speed is not the speed below which an aircraft immediately stalls?
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Old 11th Jul 2017, 06:48
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Fork tail and Hiway have obviously never spent the time to master or enjoy the eccentricities of the family of Austers. Takes a while but worth it. All have their own quirks of the Mark.
Press 'Like' for Austers !!

I see at the local field modern spamcans getting bent; wheel-barrowing, dropped in, or long floats with bounds ending in dinged props, flat tyres and bent nose legs.
They all have their requirements for piloting skills.! Just like Austers.

And on the short field note.. In the "Drover" POH the instruction was...
'Land as normal and carefully apply the brakes'
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Old 11th Jul 2017, 08:06
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I can't remember the last time I looked at my ASI on short final.
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Old 11th Jul 2017, 08:26
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Originally Posted by ForkTailedDrKiller View Post
I have never considered flying an Auster to be a pleasure! The least favourite aeroplane in my log book.
Well, I have more than 450 hours in mine now and have flown from one end of the country to the other in it. I think I have learned a little about flying it but I know there is a lot more yet before I can do it right all the time.

Yes, it's a tad cramped inside. The heel brakes aren't brilliant. The flap lever can be a challenge for anyone in the right hand seat. The view out front is a little obscured until the tail is flying. Those bungees... BUT it can land almost anywhere. It actually flies quite nicely. It is forgiving in the air (but not on the ground). It carries a fair load. And it crashes really slowly.

Perhaps you just didn't try hard enough, FTDK? Or perhaps you tried too hard?

Kaz
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Old 11th Jul 2017, 08:36
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Originally Posted by aroa View Post
Fork tail and Hiway have obviously never spent the time to master or enjoy the eccentricities of the family of Austers. Takes a while but worth it. All have their own quirks of the Mark.
Press 'Like' for Austers !!

I see at the local field modern spamcans getting bent; wheel-barrowing, dropped in, or long floats with bounds ending in dinged props, flat tyres and bent nose legs.
They all have their requirements for piloting skills.! Just like Austers.

And on the short field note.. In the "Drover" POH the instruction was...
'Land as normal and carefully apply the brakes'
LIKE!

They have done mining surveys in extreme temperatures (Lang Hancock). Some were aerobatic. They have operated from water on floats. They have worked in alpine areas and Antarctica on skis. They were launched from Landing Craft with JATO bottles. They were used by Army and RAF for just about everything. that wasn't direct combat. And Johnie Johnson managed to evade an Me109 in one!

Kaz
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Old 11th Jul 2017, 09:21
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Perhaps you just didn't try hard enough, FTDK? Or perhaps you tried too hard?
I towed gliders in a J5B (My initial tailwheel endorsement) and have time in a J1B and a J5F - I just don't like them!:

Dr

Last edited by ForkTailedDrKiller; 11th Jul 2017 at 09:32.
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Old 11th Jul 2017, 10:01
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Close the throttle, hold the stick back into the prestall buffet, keep the wings level with rudder and note the extremely high sink rate, at about 20 feet above your selected landing area give it a large amount of throttle to arrest the sink just above ground level, close throttle, land, apply brakes, be amazed at how short you have landed. Easy peasy.
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Old 11th Jul 2017, 11:23
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Shortest landing should have full power on with wheels at ground + 2ft, about 20 ft before end of runway/paddock. Dependig on power available and wing loading/design, airspeed can be stall - 10kts at that point. Closing the throttle/s wil result in an immediate and "firm" touchdown. Try a fully loaded (maybe a bit more than fully) Aztec into 1600 ft of strip with 15 kts of tailwind and a vertical rockface for the over-run. No possible go-round, great incentive to stop short.
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Old 11th Jul 2017, 11:25
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Originally Posted by Lead Balloon View Post
I hope we all realise that stall speed is not the speed below which an aircraft immediately stalls?
And.....





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Old 11th Jul 2017, 11:26
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Ref approach speeds, consider that, for a light civil certification, the OEM is only going to do that which is required by the design standards to show compliance. There may be other, data gathering, flights undertaken but the user out on the real world can't be sure of that or what, if any, data may have been obtained.

Basically, if one operates outside what is in the AFM/POH, one ought to presume that one is experimenting and may come across the odd surprise here or there.

For me, short field on a civil lightie, is an approach and landing as per the speed schedule and technique described in the POH.

(... yes, I know, we've all done it and it was great fun .. but, perhaps, we ought not to have done so ? If the evidence is there for the inquiry, subsequent discussions might not be pretty at all)

Different ball game for a military certification ...

I hope we all realise that stall speed is not the speed below which an aircraft immediately stalls?

.. if one does it the way the OEM FT folk did it .. then my money is on it having much the same sort of result ... However, the usual training stall is not the certification stall so I guess that is where your comment comes from ? That's not to suggest that the usual training stall makes much sense but that's the way it is, I guess.
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Old 11th Jul 2017, 11:27
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Oh, and I meant to say I totally agree with Step turm's last line, but some places weren't normal.
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Old 11th Jul 2017, 12:52
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Doesn't stall speed coincide with the stall angle of attack, and the stall angle of attack coincide with the maximum lift coefficient?
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Old 12th Jul 2017, 00:50
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Step turn, I agree with most of what you are saying, and you do need to have the right boxes ticked.
1. Light winds
2. Operational necessity
3. An aircraft that has a shorter take off than landing, and
4. A lot of experience in the aircraft and good currency.
As risk mitigation, the drag it in with power won't get you in short over the trees, a side slip would need to be to ground level and would still give you a float. However if you drag it along with power till past the trees, then ease of the throttle to let it sink, arrest the sink at the right time with with smoothly increasing power you get a much more controlled descent. If you give it a large quick application of power at the last possible moment you will land a few feet shorter but with a greater risk of miscalculation. Once you get it there you still need to get it out again which may mean starting the take off roll in an entirely different direction to the direction you will be pointing when you lift of.
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