Short Field Landing Airspeed Conundrum

[Centaurus]

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:ok:

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..

[cyclic35]

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.

[spinex]

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.

[ForkTailedDrKiller]

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.

[Flying Binghi]

...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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[hiwaytohell]

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!

[ACMS]

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.

[Lead Balloon]

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

[aroa]

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'

[lo_lyf]

I can't remember the last time I looked at my ASI on short final.

[kaz3g]

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

[kaz3g]

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

[ForkTailedDrKiller]

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 :8

[flywatcher]

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.

[FL235]

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.

[Flying Binghi]

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

And.....;)





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[john_tullamarine]

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.

[FL235]

Oh, and I meant to say I totally agree with Step turm's last line, but some places weren't normal.

[Lead Balloon]

Doesn't stall speed coincide with the stall angle of attack, and the stall angle of attack coincide with the maximum lift coefficient?

[flywatcher]

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.

[ACMS]

Perhaps pick a bigger more suitable landing area or get a Helicopter license.....:D

If it's an emergency then it's still better to run into the rough the other end at 20 kts than stall and drop a wing and cartwheel at 100' on final trying to be smart.

Follow the POH techniques.

Or even better try not to get yourself into a situation where you "need" to land at an Airstrip that ain't long enough in the first place.......now there's a novel idea.

[flywatcher]

Perhaps pick a bigger more suitable landing area or get a Helicopter license.....:D

If it's an emergency then it's still better to run into the rough the other end at 20 kts than stall and drop a wing and cartwheel at 100' on final trying to be smart.

Follow the POH techniques.

Or even better try not to get yourself into a situation where you "need" to land at an Airstrip that ain't long enough in the first place.......now there's a novel idea.

It might not be a case of needing to, it might be a case of just wanting to.

[ACMS]

So you advocate landing at a strip too short for your Aircraft because you wanted to.

Ok then I'll watch from the sidelines with my camera, good luck..:=

[Tankengine]

Doesn't stall speed coincide with the stall angle of attack, and the stall angle of attack coincide with the maximum lift coefficient?

Close, but no cigar!

Stall angle of attack is greater than that for max lift coefficient for obvious reasons. Even textbooks get this wrong sometimes, you need to look at polar curves.

[Tankengine]

Perhaps pick a bigger more suitable landing area or get a Helicopter license.....:D

If it's an emergency then it's still better to run into the rough the other end at 20 kts than stall and drop a wing and cartwheel at 100' on final trying to be smart.

Follow the POH techniques.

Or even better try not to get yourself into a situation where you "need" to land at an Airstrip that ain't long enough in the first place.......now there's a novel idea.

There is a whole industry in North America around stol aircraft, for FUN!
Not everyone wants to cruise around in a spam can or plastic speedster.

[Lead Balloon]

Close, but no cigar!

Stall angle of attack is greater than that for max lift coefficient for obvious reasons. Even textbooks get this wrong sometimes, you need to look at polar curves.And what is your definition of "stall"? Your "obvious reasons" are "obvious" in the case only of the intuitive definition of "stall".

You'll forgive me if I continue - for the time being at least - to believe that the authors of Aerodynamics for Naval Aviators got it right.

[flywatcher]

So you advocate landing at a strip too short for your Aircraft because you wanted to.

Ok then I'll watch from the sidelines with my camera, good luck..:=

Been doing it for over 55 years, never scratched one yet.

[Capn Bloggs]

authors of Aerodynamics for Naval Aviators got it right.
Sure did: power for slope and pitch for speed. :ugh: := :rolleyes: :}

[Lead Balloon]

How would you adjust speed in a glider, Cap'n?

[Capn Bloggs]

As I said, on and on and on... Go for a walk, LB.

[john_tullamarine]

Doesn't stall speed coincide with the stall angle of attack, and the stall angle of attack coincide with the maximum lift coefficient?

Hurt tells a good story. However, g is very relevant to what goes on betwixt IAS and stall so one really needs to specify just what is what for the stall.

[Tankengine]

And what is your definition of "stall"? Your "obvious reasons" are "obvious" in the case only of the intuitive definition of "stall".

You'll forgive me if I continue - for the time being at least - to believe that the authors of Aerodynamics for Naval Aviators got it right.

Believe what you like, in this case wrong.
Didn't know you were a naval aviator (that is a promotion from pilot right?) ;)
Some people do have an odd idea of what a "stall" is, might explain some of the instructional techniques out there! ;)

[ACMS]

Tankengine:----yes I agree there is a range of STOL Aircraft but they have approved techniques in the POH to do their STOL landings with P charts to suit.

A standard lightie doesn't.

[Tankengine]

Tankengine:----yes I agree there is a range of STOL Aircraft but they have approved techniques in the POH to do their STOL landings with P charts to suit.

A standard lightie doesn't.
True, but then if you use the POH to find the approach speed for a standard lightie it will probably be 5-10 knots slower than the "instructor approved" speeds these days. ;)

[Lead Balloon]

I see it now. On the subject of short field landings, who'd be silly enough to draw on the knowledge and data derived from the people who land very fast jets very accurately on very short ships?One important fact to be appreciated is that the airplane ... stalls at the same angle of attack regardless of weight, dynamic pressure, bank angle, etc. Of course, the stall speed of the aircraft will be affected by weight, bank angle, and other factors since the product of dynamic pressure, wing area, and lift coefficient must produce the desired lift. ...That's why stall warning devices usually sense angle of attack or pressure distribution, not airspeed.

And oddly enough, the definitions of Vs and Vso in the fairly vanilla POH I have in front of me for a fairly vanilla aircraft do not say the speed below which the aircraft stops flying.

Good luck staring at the ASI and using power to manage airspeed to nail that perfect short field landing!

PS: I have been lucky enough to spend some time with an instructor like this one (whom I quoting from the backcountrypilot.org website):I would suggest that if you want to get comfortable with short strip flying it is good to get comfortable at going slow. I am our company's instructor, and in the first flight with every new company pilot I cover the airspeed indicator, load the plane to gross (about 1100 lbs) and we spend a half hour flying with the stall horn on, clean and dirty, 30 degree banked turns clean and dirty and a descending dirty turns to left and right.

[ACMS]

Tankengine:---- KISS method to keep it simple for low hour Pilots. 65kts full flap for a PA 28 is what the P charts say at max weight so that's the speed they were taught to fly. Yes it's a little fast by around 10 kts at light weights.

In an ideal world each landing would be checked for weight and conditions and a suitable VREF selected however that gets a little complicated for newbie Pilots.

If you need to land on a short strip in the bush then you should consult the P charts and fly the speed BUT this is not a short field landing.

Anyway....

[john_tullamarine]

yes I agree there is a range of STOL Aircraft but they have approved techniques in the POH to do their STOL landings with P charts to suit.

I don't see anything in the certification standards for civil STOL. Can you post some specific POH technique words and a P chart or two to support your contention ? I'm only too happy to learn something new ...

Now, what an operator with a need might choose to do is another story altogether ... then it becomes an interest for the Regulator and the insurer.

Military is a different arena.

[cooperplace]

How would you adjust speed in a glider, Cap'n?

push the stick forward? or back? air brakes?

[Tankengine]

push the stick forward? or back? air brakes?

All three will work, of course using the last may well kill you!
An A380 Captain embarassed himself by using the wrong technique a while ago then made it worse by telling everyone unknowingly at briefing! ;)

[cooperplace]

All three will work, of course using the last may well kill you!
An A380 Captain embaressed himself by using the wrong technique a while ago then made it worse by telling everyone unknowingly at briefing! ;)

of course; I use all 3 as required when I'm in the Grob.

[ACMS]

John:---- there are civilian Aircraft designed for their short takeoff and landing ability aren't there? They will have a POH describing correct procedure/technique for landing that Aircraft which is a "normal" landing for that Aircraft. They will have P charts as well detailing LDR etc.

That's all I meant mate.

I didn't mean to infer that there is a special "STOL" technique mentioned in their POH, as all landings in that type are STOL and thus normal to the them.

Ok

[john_tullamarine]

I think you might have missed my point .. STOL is a military animal. Can you cite a civil aircraft which has a STOL certification ? Not looking at what one might be able to do with them but some certification data in an approved AFM/POH ?

Just interested to know if any such do actually exist.

[ACMS]

No John unfortunately I'm not an expert in civilian or military certification standards. But there are quite a few out there are known for their STOL capabilities in their design and performance characteristics.

What about the civvy Pilatus Porters meat bombing around?

What about the Twin Otter it's also known as a STOL Aircraft, renowned for its abilities.

Either way certified with STOL capabilities or not they need to be operated in accordance with their POH and P charts.

We are probably arguing over a term.

[john_tullamarine]

We are probably arguing over a term.

Yes ... and, no.

The civil certification standards (eg FAR 23) impose margins above stall to give the operation a reasonable chance of surviving problems .. such as turbulence, engine failure, etc.

The military approach acknowledges that there will be operational requirements which dictate operating to a higher level of risk and mishap probability .. ie lower speeds and lower margins above stall. As would be expected, the usual military certification and release to service protocols spend a lot of time and effort in providing crews with detailed information regarding just where the boundary limits are for such operations.

The uncomfortable risk with many civil operations purporting to be quasi-STOL is that this FT work up work isn't done and the pilot is put closer to real operational limits than the civil design standard protocols envisage.

Civil and military certification .. two very different animals.

I would expect that the operational documentation for civil versus military operations on the two aircraft you cite might be quite different in detail ?

Perhaps others who have access to both sets of data might be able to comment ?

Certainly, the POH approved data can be expected to comply with the nominated standards.

[ravan]

Maybe I'm missing something in this discussion, but the Information Manual for the 1980 Cessna C172 N Skyhawk (for example) which I have on my bookshelf, gives tables in Section 5 (Performance) for Take-off and Landing distances based on Short Field Technique as specified in Section 4...??
Section 4 (Normal Procedures) goes on to give the techniques for short field and normal take-offs and landings.

[HarleyD]

JT is, as usual, correct and also displaying his measured and conversational response.

TAke off, and landing, performance is determined in accordance with the rules laid out in the FAR

(a) For normal, utility, and acrobatic category airplanes, the takeoff distance must be determined in accordance with paragraph (b) of this section, using speeds determined in accordance with §23.51 (a) and (b).

(b) For normal, utility, and acrobatic category airplanes, the distance required to takeoff and climb to a height of 50 feet above the takeoff surface must be determined for each weight, altitude, and temperature within the operational limits established for takeoff with --

(1) Takeoff power on each engine;

(2) Wing flaps in the takeoff position(s); and

(3) Landing gear extended.

(c) For commuter category airplanes, takeoff performance, as required by §§23.55 through 23.59, must be determined with the operating engine(s) within approved operating limitations.

[Doc. No. 27807, 61 FR 5185, Feb. 9, 1996

This is not the latest amendment but adequate for reference.
Once the speeds determined in 23.51 have been determined they are applied to the procedure defined in AC23-8C. Note, the reference speeds used are minimums and the manufacturer may choose to vary them up, and lengthen distances, but not reduce them to in order to Shorten Take Off or Landing.

As the FAR and the AC has been reviewed and amended to higher standards over the years even more prudent procedures and tolerances have been introduced which means the exact same aircraft designed many years ago would have longer distances in the POH if it is done to latest standards. Nowhere is a procedure that reduces to prescriptive methodology mentioned.

TOL distances are THE distances and the POH is required, these days at least, to specify the method that the pilot must use it achieve the chart performance numbers. Vr, or rotation speed, the speed at whihich the pilot may apply the control input intended to raise the nose wheel clear of the pavement, is determined and included in the procedure specified in the POH.

So, STOL does not apply to civil aircraft, although techniques intended to minimise ground roll, if applied may provide improved numbers.

The AC states that technique used for the charts is NOT to be one that requires exceptional skill and/excessive forces, but that that can be emulated by a normal or average pilot. This includes references in the procedures to not require doing two actions simultaneously, and deliberately introducing small delays between actions during the testing process.

Fly the procedure in the POH, get the numbers and power settings perfect and book numbers are readily attainable, be well practices and react quickly, raise flaps immediately after touch down, and you may even achieve shorter distances, but without reducing the speeds, and energies, physics will basically rrule this equation.

Testing, and the book numbers require the vehicle to be over max weight, and slightly forward of max fwd CoG for all tests as an additional factor so that the numbers are conservative in any case. Manufacturers, not in this country, have been known to run engines in specially and ensure that although the engine has time on it, it is measured to optimum wear specifications and making best power. Brand new engines are the most sluggish until they have loosened up, and do not typically provide best performance. Heritage US manufacturers often gamed the system, which is why the rules are much tighter now.

Vr, Vtoss, Vy, Vx, and Vref are all factored for weight in modern certifications, but not for CoG, so performance can be slightly improved with an aft loading, which is not accounted for in the charts.

HD

[john_tullamarine]

.. the Information Manual for the 1980 Cessna C172 N Skyhawk ... gives tables in Section 5 (Performance) for Take-off and Landing distances based on Short Field Technique as specified in Section 4...??
Section 4 (Normal Procedures) goes on to give the techniques for short field and normal take-offs and landings.

A quick net search came up with a 1980 POH dated July 1979 with no revisions affecting relevant pages.

The point in question, here - what are the take off and landing speed schedules for the two techniques - short field and normal ?

Looking at the POH, above, one gets

for "short field" takeoff Vtoss = 1.12-1.21 Vs
for "short field" landing Vapp = 1.34-1.43 Vs

with the range quoted depending on CG for gross weight. The figures quoted are from my sums .. while I have nominated two decimals, the reality is that one should not read to that sort of apparent precision .. so, looking at the forward CG - which is the more critical - one would have approximate margins of, say, 1.2 and 1.4. The usual 1.3 for approach is a minimum and the OEM is perfectly entitled to run a bit faster .. that probably indicates that the TPs were of the view that coming in over the fence with only the maker's name on the clock might not be a really bright idea. If you are of a mind to check my numbers, do remember to apply PECs so that the calculations are done with KCAS rather than KIAS.

These figures are pretty close to the normally seen civil certification margins so, it follows, these "short field" operations are what most of us with a certification background would consider normal operations and, certainly, not STOL.

That the OEM elects to refer to the techniques as short field and normal is neither here nor there .. we are talking about certification operations (short field) and a more comfortable higher speed operation recommended by the OEM (normal) .. but not STOL in any sense of the term.

Unfortunately, the Industry is beset by lazy terminology ... (and, I have to admit, I'm just as lax and lazy at times, myself).

If you want a feel for STOL, you could go not much further than carrier operations .. I note that Centaurus, in the first post, makes reference to his experiences in the Sea Fury .. hairy stuff. As a sideline point of interest, another PPRuNe poster (Milt) was the chap who sent Centaurus off for his first Sea Fury jolly all those years ago ...

[aroa]

STOL a military animal....que..?

Old Sybl..VH-SIB was a TU-206 with a Robertson STOL conversion. Modified leading edge, droopy ailerons with the flaps, extended wings. Had been operated with SIL / Summer Institute of Linguistics in the highlands of PNG. STOL capabilities being the go for the "airstips" there. Could certainly do the tight spots ok.
A Higher Authority trod on it in the BNE super cell storm Jan 1986. Vale SIBL.

There is a Wren Cessna 180 about, also a STOL conversion.
I guess they were certified as per the mods for STOL ops.

These days there are 'flying ' gadgets about for off field landings like the LSA Highlander STOL. Bit of a breeze and its landing run = length of the aeroplane !!
I want one .

[john_tullamarine]

STOL a military animal....que..?

That's the general story.

Robertson STOL conversion

I have no specific familiarity with the Robertson mods. However, I suggest that what they do is reduce the stall speeds which, in turn, reduce takeoff and approach speeds while maintaining the usual certification margins above stall. This then reduces runway requirements. Fine to market that as STOL but it is not what STOL design is, per se.

I am happy to be proved wrong in respect of the certification .. but that will require a copy of the relevant approved POH which will tell the story in some detail.

Real STOL, as the military do things, is a different animal which operates much closer to stall and accepts a considerably higher probability of mishap in the event of something going awry. The benefit is a shorter distance requirement. Acceptable for some operations in the military but not for routine civil operations.

in the highlands of PNG

Now, I don't have any information regarding the specifics for the aircraft Type in PNG ... but do keep in mind that the old DCA rules were a tad different for developmental operations in PNG ... so it may be a case of comparing apples and oranges. It's so long since I had a look at the old rules .. the poor old memory is not up to recalling the details now.

[kaz3g]

of course; I use all 3 as required when I'm in the Grob.

And a very nice little MG it is, too!

[john_tullamarine]

Re my comment earlier about Milt and Centaurus .. the memory played tricks .. Milt sent C off on his first Mustang jolly ...

[LeadSled]

AAAAH!! The Wren.
Mate of mine has a lovely Wren 182 (they have their own Type Certificate, as I recall, more than just a bolt -or glue on mod.) and he has even screwed a few more horses in the front by way of an IO-550 -- what a seriously fun aeroplane to fly.

As for the whole discussion, there is what you "can do", what is wise to do.

If it all goes wrong, it will be between you, your god, your insurance company, and CASA's rather variable (depending on their desired "policy" outcome) application of CAR 138.

Bloggsie,
Your interpretation of the venerable US Naval publication and how to fly an approach in larger turbine aircraft (but it works for any aircraft) certainly explains a lot??

Tootle pip!!

[Stationair8]

Had the pleasure of flying a C172 with a Robertson kit fitted to it.

The owner bought it new, picked it up from the factory and then flew it to a maintenance organistation to get the Robertson stol kit fitted.

There has been a few Robertson STOL Cessna C206's imported into Australia over the years, good idea to get an experienced operator to show you the finer points of operating with the STOL kit.

[LeadSled]

Stationair8
Having flown a number of C-1 or 2XX over the years, believe me, a Wren is a whole different level of "STOL" .Sorry, JT, but I think, in my MNSHO that STOL could long since be regarded as a generic term, certainly based on old brochures for civil aircraft out in the back shed.
At one stage (thanks to Bloggsie) I thought we were going to have a whole new round of "Attitude controls airspeed, power controls rate of climb or descent" versus "attitude controls flightpath (or aim point), power controls speed" but that one seems to have died.
Tootle pip

[Stationair8]

Yes LeadSled, I wondered why the owner would actually put a STOL kit on a C172!

The Wren does sound an interesting piece of kit.

[Capn Bloggs]

Your interpretation of the venerable US Naval publication and how to fly an approach in larger turbine aircraft (but it works for any aircraft) certainly explains a lot??
Those of you who think you know everything are annoying to those of us who do... :} :ok:

[john_tullamarine]

STOL could long since be regarded as a generic term

.. of course it is .. but the younger chaps and chapesses, at the very least, ought to have the subtlety brought to their attention ..

[LeadSled]

Sure did: power for slope and pitch for speed.
Bloggsie,
Given the rather confused variety of emojis in that post #30, are you suggesting the above is right or wrong??
Please elucidate.

JT,
Having given this some thought, I think a time warp is the problem.

"Back in the day" (before aircraft had an AFM as we know it today, and "handling notes" were rudimentary) a "normal" approach was a glide approach, with "enough" IAS for a short float in the flare before your stalled the aircraft onto the ground.

Indeed, in honour of this "normal" approach, all the RAC/NSW Gipsy Major or Cirrus powered aircraft had the carb.hot air locked on, which did "wonderful" things for performance when you actually needed the power.

A "precautionary approach" as per the syllabus (Pub. 45 and predecessors) was a prelude to an out or forced landing due (usually) weather, and included practicing/demonstrating a low level circuit to determine where you were going to land, followed by a "power on" approach at a somewhat lower IAS than "normal". all aimed at an accurate touchdown at the chosen point.

Seems to me that the present application is to demonstrate an approach at the "right speed" ie; the AFM speed, versus the excessive speed I observe being flown on a "normal" but always now power on, approach.

But, Hey !! Bloggsie, what would I know, compared to Aces of the Bases like your good self, I am happy to admit I am still learning.

Tootle pip!!

[Capn Bloggs]

Just fly it like the autopilot does, Leddie, and you won't go too far wrong (ie low or slow)! :ok:

[Sunfish]

C172 N POH states stalling speed not more than 44kias at MTOW at 30deg bank. recommended short field is flaps 40deg at vref 60 kias. that's at least 1.36 Vs. lighter weight and smoother conditions could see verified at 55 kias flaps 40 and stall say 40kias that's still 1.37 vs. that's a ground roll of about 550ft on pavement. Worst case 44kias stall and 55 Vref is still 1.25 Vs. I guess one could say that the POH is conservative.

However since groundroll on takeoff is probably at least 850 ft then barring emergencies, it's all a bit of a moot point isn't it?

[john_tullamarine]

C172 N POH states stalling speed ...

.. except one doesn't do these sums with IAS .. speed calcs need to be in CAS with PEC corrections as/when appropriate to get to/from IAS.

IAS is a Mickey Mouse number ... very useful for reference as it is all we can see when pushing and pulling .. but it is still a Mickey Mouse number, not relevant for running sums.

More interestingly, once down towards stall, PECs can get a bit average .. run the sums in CAS and then see what the margins might be ...

[LeadSled]

Just fly it like the autopilot does, Leddie, and you won't go too far wrong
Bloggsie,
And which model of autopilot would that be, in which mode, in which aircraft.
Instead of the cryptic nonsense, explain what you mean (if, in fact, you understand yourself) what you actually mean in post #30.
Tootle pip!!

[Capn Bloggs]

Leddie, I think you are trying to bait me into derailing the thread! Tut Tut. Suffice to say that the AFNA statement that ones uses power to control the approach path (p360-ish) is, in my view, Horsesh1t! :ok: Re the autopilot, it doesn't actually matter which type; I was referring to the autopilot's/autothrottle's technique for flying down final on the ILS.

Now, back to normal programming...

[Sunfish]

JT, thank yoU, one more thing I didn't know and nobody taught me. The margins are lower when calculated in KCAS. The 60 vref/44 vs goes to lowere to perhaps 1.3 in kcas. The "worst case" 55kias/44vs goes to about 1.13VS when calc'd in KCAS.

[Lead Balloon]

Leddie, I think you are trying to bait me into derailing the thread! Tut Tut. Suffice to say that the AFNA statement that ones uses power to control the approach path (p360-ish) is, in my view, Horsesh1t! :ok: Re the autopilot, it doesn't actually matter which type; I was referring to the autopilot's/autothrottle's technique for flying down final on the ILS.

Now, back to normal programming...It's actually at page 27:This fact provides a fundamental concept of flying technique: Angle of attack is the primary control of airspeed in steady flight. Of course, the control stick or control wheel allows the pilot to control angle of attack and, thus, control the airspeed in steady flight. In the same sense, the throttle controls the output of the powerplant and allows the pilot to control rate of climb and descent at various airspeeds.

The real believers of these concepts are professional instrument pilots....And to return to the central theme of this thread: At the stall speed, an aircraft is still flying.

[john_tullamarine]

The margins are lower when calculated in KCAS.

Calculations based on IAS are a bit meaningless due to the system errors, especially down around the stall region..

With CAS you will get a reasonable idea of what the numbers are. The FT folk will be doing things to the best accuracy their kit permits and, with round off, etc., your calcs might be a little rough for small aircraft .. but, nonetheless, adequate for the task.

[aiming point]

Pffft, too easy:

https://www.youtube.com/watch?v=SJ22dCkDr7Q

Into the flare, just retract the flaps and get it on the ground.

[Flying Binghi]

Pffft, too easy:

https://www.youtube.com/watch?v=SJ22dCkDr7Q

Into the flare, just retract the flaps and get it on the ground.

Eerrm... lucky there's no wind about. Also, didn't seem that short for a 182.

Reference light aircraft - Don't know why people 'stabilise' the min approach speed so far out thus exposing themselves to 'stall' incidents. IMHO, Yer only need that min speed seconds before touchdown.






.

[djpil]

The data presented in the performance section of the POH is obtained with "average" piloting skill ...Nope, that only applies to aircraft certified in relatively recent times. My airplane was certified to FAR 23 as of Feb 1965 which only required "must be able to be landed safely and come to a stop without exceptional piloting skill."

The civil certification standards (eg FAR 23) impose margins above stall to give the operation a reasonable chance of surviving problems .. such as turbulence, engine failure, etc.Nope, not necessarily. That FAR 23 of 1965 did not require landing distance to be determined nor did it specify the minimum landing approach speed.

Certainly, the POH approved data can be expected to comply with the nominated standards.Yep, but one must know the nominated standard. The manual for my airplane states a stall speed of 47 kts and a landing approach speed of 52 kts. Maintenance standards allow my ASI within 2 kts so that would get me to within 3 kts of the stall speed stated. Even 1 kt out reduces approach speed at 50 ft to 1.09 x stated stall speed.

CASA's MOS for a tailwheel endorsement mandates that the trainee demonstrates that he/she do better than the unfactored distance in the manual - what a joke.

[Centaurus]

Reference light aircraft - Don't know why people 'stabilise' the min approach speed so far out thus exposing themselves to 'stall' incidents. IMHO, Yer only need that min speed seconds before touchdown.



Agree. RAAF training post war was the approach was standard profile until 300 feet then deliberately reduce speed to planned figure for precautionary landing ie about 10 knots below normal approach speed.

[spinex]

All getting a bit esoteric for my little peabrain. My ASI reads IAS and I tend not to fluff about with whizzwheels and what have you when trying to plant the wheels as close to the downwind end of the runway as possible. A reasonable margin above the number where she normally adopts a more downward trajectory generally suffices. As for the old chestnut about attitude for speed etc, I tend to come down on the side of the little Mexican lass; "why not both?" Most of us have mastered (I hope) secondary effects of controls and tend to apply that combination of inputs required to achieve the desired result. Teaching attitude for speed is all very well as a teaching device, but imo is not to be slavishly adhered to once one has a degree of familiarity with placing said aerial device back on terra firma.

[Lead Balloon]

<snip> Teaching attitude for speed is all very well as a teaching device, but imo is not to be slavishly adhered to once one has a degree of familiarity with placing said aerial device back on terra firma.Indeed.

Except in the case in which you have to do a real short field landing. :ok:

Agreed re the ASI, too. Folks who want to do real short field landings would give up an ASI for an AOA indicator, any day.

[Tankengine]

Try doing pitch for aim point and airbrakes for speed in a glider, and some lighties, and eventually you will die.
I do it in a heavy jet and it works fine. ;)

[john_tullamarine]

Yep, but one must know the nominated standard.

Indeed, Dave .. which is why we often make reference to the TCDS in an endeavour to get folks to look these things up.

Overall, posts here have to be a bit truncated (otherwise we'd ramble on for pages and no-one would bother reading ..).

As a result, we don't cover all the ins and outs in great detail...

[megan]

Those who specialise in short field (carrier guys) are taught pitch controls AoA, and hence airspeed, power controls altitude (ROC/ROD). Though airspeed is mentioned, AoA is the prime instrument, located on the canopy bow so no need to go heads down. See at 4:50 for power variations (exhaust smoke) to maintain slope.

FqzlNILBgbM

[Lead Balloon]

And just to reinforce another point about why AOA is so important (and such useful information if you can get it) when doing real short field landings: An aircraft stalls at the same angle of attack regardless of weight, dynamic pressure, bank angle, etc.

[Flying Binghi]

Those who specialise in short field (carrier guys)...

Whilst i think aircraft carrier flying is the most demanding of pilot skill and stands at the panicle of aviation endeavours, i would argue that it is not entirely comparable to landing in a padock.

For us land lubbers it would be nice to be able to 'adjust' the runway so that all landings are into wind. Also nice to have a cast of thousands to assist with take-offs and landings - especially nice to have somebody accessing each landing and giving a wave-off if things don't look good. Allso good to have an arrester hook to hide any small landing errors... The other thing is normally over water the air is so clear of turbulence that even a plump turkey like julia gilLard could fly.





.

[megan]

Allso good to have an arrester hook to hide any small landing errorsThere is no hiding anything. Landings/approach are graded by the LSO, and a board in the crewroom keeps tallie of your record for all to see. As well as that, your approach to touchdown is broadcast on the ships video, with crosshairs on the screen denoting the glideslope, see video. Any deviation is obvious to all. Absolutely nothing hidden, and the LSO in his debrief will tear strips if required.normally over water the air is so clear of turbulenceTurbulence from the carrier is a very real issue, and would bring your fat turkey undone in a flash.

SPlqoeaPUu4&t=516s

[LeadSled]

Folks,
Now I will set the cat among the pigeons.

A teaching technique that applies to large aircraft (but Bloggsie wants to dance around the point) is to use "attitude controls climb and descent, power controls airspeed".

With some special variations not applicable here, and not applicable in RVSM airspace ever, this is exactly what modern (in fact almost all) autopilots do, and it applies equally well to a voice activated autopilot's hands and feet.

Indeed, many moons ago, when I had an ab nitio student who was having trouble with "attitude controls airspeed, power controls rate of climb or descent" I would dump the "approved" as preceding, and use as para1.

Indeed, I would go so far as to set a PA-28/C-172/whatever up on final, on speed and height/slope, and use a chinagraph pencil to arrange a "gunsight" cross on the windscreen and set on the aiming point on the runway.

Then: "Just keep the cross on the aiming point (usually the threshold marks on a sealed runway) and fly XX knots with the throttle". The transition to flying a stable approach, on speed, on slope,was rapid, and for students I can well remember, the boost to their confidence was (to them) remarkable, but to me, expected.

Indeed, one (then) young lady who had already done about 18 hours with another school, without looking like ever going solo, was off solo with us in a couple more hours. Said young lady suddenly really started to enjoy flying, to the degree that she decided to make it a career, went through to commercial with us. Last time I heard, she was an IRE/TRE flying seriously large machinery, a long way from the point where she was about to give up, until somebody suggested she change schools --- because "the other mob" did things differently" --- which we certainly did.

Going back to my "time warp" comments, "back in the day" in GA, all approaches were glide approaches, attitude certainly did control airspeed da-da da, and a burst of throttle or a side-slip, if/when necessary, to (in modern parlance) adjust the touchdown (another way of saying the aim) point, give or take for a flare and float.

That you can fly all aircraft the same way, (even a delta) regardless of size, seems to be lost on quite a few.

I most certainly agree about the primary importance of angle of attack, if you are on approach, on slope and on speed, you will have the desired angle of attack for that operation.

All the modern FAR 25 aircraft, of which I have a detailed knowledge, all have a series of inputs into an Air Data Computer, beyond just raw pitot and static pressure/temperature, and will include angle of attack and where available, inertial acceleration/deceleration, to compute and display IAS (effectively CAS), low speed limits and generate "stall" warnings, that are not "stall" warnings at all, but low speed warnings.

As some of you will be aware, "Vs" is no longer the basis for establishing various V reference speed for larger FAR 25 aircraft, such speeds are based on an increment above the Cl max. angle of attack CAS. For approach, that Vref is generally 1.2 Cl max CAS.

So, where does that get us, flying a light aircraft (FAR 23 or predecessor CAR) and being asked to demonstrate a "precautionary" or "short field" approach versus a "normal" approach.

There is a good argument to make, that there is no such distinction, what is being "demonstrated" is the ability to fly an approach at the "book Vref" IAS, instead of the generally quite excessive IAS speed all too often called "normal".

You should NOT be expecting/required to demonstrate a "different" approach when the landing field length is critical, if you fly the book figures for every approach (with a small allowance for gust), that becomes your "normal", and the day you fly into your mate's farm, or you have to land somewhere due, say, stress of weather, you will have no concern about you ability to fly the approach. You must have a "reasonable" margin over "the stall", the "Book" speed gives that, and it is always lower risk to roll off "the other end" at slow speed, than lose control on approach.

In the "Half MVsquared" world it is the Vsquared wot gets ya on a bad day.

[Capn Bloggs]

"Always remember and forever take heed: left hand for glidepath and right hand for speed!" (reverse for First Officers and those hanging on to the stick between their legs or with throttle centrally on the dash...). :ok:

[Tankengine]

"Always remember and forever take heed: left hand for glidepath and right hand for speed!" (reverse for First Officers). :ok:

Works well for single seaters! ;)

[LeadSled]

"Always remember and forever take heed: left hand for glidepath and right hand for speed!" (reverse for First Officers). http://cdn.pprune.org/images/smilies/thumbs.gif

Bloggsie,
So predictable, but you always did have your hand on it.

As it happens, that would work for all the aeroplane I flew originally, as the throttle was always on the left ---- indeed, the RAF was so keen on the idea of the throttle being in the left hand side (rather traditional in single seat or tandem aircraft) that even some trainers with newfangled side by side seating had two sets of throttles.

One undeniable fact remains, an autopilot on a couple approach (or any time, really) uses power/thrust to control speed, and pitch to control climb and descent ---- and there is no good reason why a human pilot should not do the same thing ---- now that powered approaches are the norm.

Tootle pip!!

[Flying Binghi]

Ahem... when yer comes out of a slip is that considered as thrust ?...;)






.

[Capn Bloggs]

indeed, the RAF was so keen on the idea of the throttle being in the left hand side (rather traditional in single seat or tandem aircraft) that even some trainers with newfangled side by side seating had two sets of throttles.
Indeed indeed. Given that the RAF is an AIR FORCE, and most airforce aeroplanes (not trash-hauling types) have the stick between the legs and throttles on the left, it is entirely reasonable that their trainers would have two sets. Just like the Ginwheel, eh Leddie?

I've always thought 1.3Vs in a Cesspit is too fast... Stick to stay on slope, and throttle to just keep the wailing cat at bay... :ok:

[gerry111]

Just like the Ginwheel, eh Leddie?:ok:

Brilliant entertainment, Capn Bloggs and LeadSled! Please keep it coming!

(I have to confess that during my only passenger flight in a RAAF 4 Flight Ginwheel during 1981, I fell asleep over Barrington Tops. (It was a warm, sunny afternoon.) My pilot, Jorge Washington rolled the aircraft inverted pulling a bit of minus G. That woke me up! Apparently he was concerned that there may have been forms that he was unfamiliar with, had I died.)

Fast forward to a couple of weeks ago. I had a very pleasant first flight in a Tiger Moth at Luskintyre. And the very same ex RAAF Winjeel is there!

[Flying Binghi]

Brilliant entertainment, Capn Bloggs and LeadSled! Please keep it coming!...

...Fast forward to a couple of weeks ago. I had a very pleasant first flight in a Tiger Moth...



Were it demonstrated to yer how descent can be adjusted by rudder..... ;)

Hmmm ....Now were that rate or angle of descent ..:confused:







.

[gerry111]

Were it demonstrated to yer how descent can be adjusted by rudder..... ;)

Hmmm ....Now were that rate or angle of descent ..:confused:
.

Yeah, but ya need aileron as well to do them sideslips.. :cool: