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Airspeed
Why does everyone tell us that a PA28, C172,C182 and many other type float along the runway during the landing??
I hear comments like "the 182 is a big glider" or "I only ever use 2 stages of flap in a PA28 but they do float a bit". There are a lot of pilots who never use the correct airspeed for the take off, climb, approach & landing. During the take off and climb, if you fly too fast you may not get to a height where a safe forced landing can be made at or close to the airfield. (where the big red fire engine lives). If you fly the approach to fast you may end up needing the big red fire engine to pull your pride and joy out of the hedge at the far end of the runway. There is this "new" school of thought that pilots seem to have adopted, add a few knots for the "crosswind" another few for only "1 stage of flap" and a couple more for your "Granny in the back" To land any aircraft it MUST be at a speed where it does NOT want to fly anymore. Any thoughts Tony |
I cant fault that !.
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Thoughts:
Not using the correct speed for take-off is probably due to lack of familiarity with the flight manual figure for the aircraft, lack of recent flying with an instructor, and lack of self briefing regarding the climbout required (is a climb at Vx necessary?) Not using the correct speed for climbing is probably due to nothing more than a preference for cruise-climb regimes rather than best rate (better vis, engine cooling etc.) Not using the correct speed for approach is likely to be due to lack of flying with an instructor, but might also be worries about keeping the speed up in a busy circuit. Not using the correct speed for landing could be due to having trained on long runways. If you learn at Netherthorpe, you are unlikely to land long on a regular basis! But ultimately, any deficiencies come down to either training or lack of discipline. I enjoy the fact that I can always improve my flying, and aim to learn and improve on every flight. |
There's no substitute for using the right speeds - especially with aircraft prone to floating, or even more with those prone to dropping like a brick.
My sadistic instructor, years ago, made me come over the fence at 100 mph (almost double the normal landing speed), then fly along the runway at 10 feet till the speed had bled off enough to land safely. A few goes at that concentrated the mind a treat. Good job the runway at Southend is nice and long! The P28R I fly now will land with a satisfying squeak-squeak <pause> squeak accompanied by a burst from the stall warner, if handled right. Get it wrong and it bounces, or floats something rotten. I think most popular singles are pretty similar. I've sat beside Timothy as he's done the same (every time) with the Aztec. It seems to work. |
Spot on, TonyR.
To land any aircraft it MUST be at a speed where it does NOT want to fly anymore. Certainly true for light aeroplanes. So why do I see so many Cessnas and PA28s banged down level and 3-point, with hardly any flare, then stopped on the brakes? These guys just haven't been taught to fly. Why not? Teach them in taildraggers? That way, sloppy technique like that would not be tolerated by the aeroplane, and they'd have to learn how to do it correctly. We'd then all benefit from lower insurance premiums; collapsed noselegs - the result of those trike 3-pointers - are not dramatic, but gthey are very epensive to fix. And every month in the AAIB reports they feature large. SSD |
TonyR I suspect flies tailwheel.
On a tailwheel aircraft the C of G is behind the mains. The result on landing a tad fast is that the mains stop descending but the C of G continues to do so. As a result the Angle of Attack increases and you soar majestically back into the sky. On a nosewheel aircraft the C of G is forward of the mains so when landing a tad fast the AoA decreases and it doesn't gp back up into the air. The nosewheel pilot is pleased with his nice smooth landing and uses the same technique next time. However his landing was not made at the correct speed and he won't achieve book figures. This could lead to some unintentional hedge trimming with that big strimmer blade on the front when he goes into a shorter field that is plenty long enough for his aircraft when flown correctly. Mike |
Maybe what's needed is some kind of a nosewheel strain gauge that will detect the three-point trike landing and alert the poor owner. It's usually the next customer who has the nosewheel collapse :(
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I do fly tailwheel, but not at the moment, I have lots of time in Cessna 180 & 185s and some in a Maule, Citabria, Chippe, Cap 10, various Cubs, and a few homebuilts.
At the moment I mostly fly a TB20 and a Rallye 100. Each aircraft has a "minimum drag speed", This is the slowest speed that the aircraft will mantain level flight at a given power setting, (just before the drag curve beats you) If you know this speed for your aircraft then it can also become your minimum approach speed. Take the Rallye, 2 up half fuel, MDS = 53mph at 2200 rpm, full flap. If I reduce power I decend, increase power again I stop the sink. With the combined use of stick and power to maintain that AIRSPEED all the way to the roundout, the aircraft is ready to land, no float and no brakes necessary. Do any of you go out and practice "slow flying"? You will be suprised how slow your aircraft will fly! Tony |
It's a favourite trick at Old Sarum. At a safe height, reduce power to below that needed to maintain level flight. Attempt to maintain level flight. As the speed decays feed in more power to achieve a target speed while still maintaining level flight.
In something like a C152 try doing it with a target speed of 60 kt, then 55, 50, 45 kt. I doubt this is accurate but I seem to remember getting it down to about 42kt with pretty near full power applied. You need to do some clearing turns to make sure there's nothing underneath you. The exercise is very similar to doing a power-on stall but with more accurate height and speed control. Mike |
At full power this does become a bit difficult and can result in a full power on stall, on a couple of occaisions I have had a cessna engine turn the airframe as well as the prop, (not for the faint hearted).
Pick a power setting about 75% and see how slow you can fly, this will usually give you a similar attitude to your landing roundout. Tony |
Tony
Where do you get this speed and power setting from, I cant find it in the PA28 or 172 flight manual Ken |
TonyR,
Each aircraft has a "minimum drag speed", This is the slowest speed that the aircraft will mantain level flight at a given power setting, (just before the drag curve beats you) If you know this speed for your aircraft then it can also become your minimum approach speed. Also what do you mean by beats you? Vimp (min power) is the best angle of climb speed for a prop and it is slower than Vimd. I assume you mean that aircraft speed becomes more unstable when slower than Vimd? The CAA recommends that the minimum approach speed is 1.3 x stall speed for your configuration. For PT flights that figure is the mandatory minimum! But that may not be the best approach speed when matched with the correct speed over the threshold (Vat). These figures are in the POH and surely should be understood and followed?? The point of increase by the 1.3 factor is to increase safety margins. This accounts somewhat for static port/pitot port errors due to the a/c attitude and configuration as you only see IAS and not corrected airspeed as well as unexpected small variations in wind direction/speed. Also, if the wind is a significantly variable or wind shear is possible I think you would be bonkers not to add a bit extra on. |
Didn't Nevil Shute design the Airspeed?
...or am I in the wrong forum? |
HWD,
What I am trying to say is that each aircraft has a "minimum speed at a given power setting". Take the rallye aircraft again, it will fly at full power in level flight at 110 mph, but it will also fly at 50 mph using full power in level flight. I don't want to get into the whole "drag curve" bit as all I am seeking to do is encourage pilots to fly better and get more satisfaction from doing it properly. Somewhere at less than full power a "safe" minimum speed can be found, this may be used as a FINAL approach speed and will avoid the unnecessary floating along the runway and may open up a lot of "new" shorter airfields to pilots (where most of the "nice" pilots live) Regular and structured slow flying practice will enhance your skills as a pilot and increase your safety during take-offs and landings, particularly from short strips. Just a few minutes at a safe altitude spent brushing up on your slow speed flying skills is better use of your flying time than bumbling around looking at the scenery. This will teach you to avoid the traps waiting during a go-around from a botched landing attempt. You will learn to safely control the aircraft close to the stall and to recognise the early symptoms. You will learn to avoid an unplanned spin due to lack of appreciation of what the aircraft is trying to tell you during a low speed manoeuvre. Your actual flight profile for practicing slow flying should be provided by your qualified flying instructor and should certainly begin with a HASELL check, every time. Stay safe Tony |
Maybe what's needed is some kind of a nosewheel strain gauge that will detect the three-point trike landing and alert the poor owner. On my CPL check ride, the examiner told me to do a flapless landing just as I had turned a tightish base for normal full flap landing (in a 172). Even after slipping the thing in, the result was crossing the threshold at 100kts.....and did I float....for 5500 feet to be exact :D I would have gone around early but he wouldn't let me, and afterwards he gave me a lecture on the importance of using correct approach speed, which was what this demonstration was all about (and that he wanted a long landing to get back to the flying club quickly as he needed a piss..still I passed). He also made me do a SF landing, but coming in at 50kts, and dumping it right on the end of the runway. The result was we stopped in about 300'. EA |
TonyR
I believe that some of the problem comes from SOME flying instructors teaching approach speeds that are too high. Why do they do this? I don't know. But when you read on other threads of people flying short final at 75kts on a Warrior, because their instructor told them to, it does make you wonder. Presumably this is 2 up, whereas the Warrior POH suggests 63kts at gross - thats a lot of excessive energy and if you don't get it off by the threshold, landing is going to be troublesome, for sure. I was taught to land with full flap initially, but my instructor (who was a recent arrival at the school) was then directed by the CFI to teach me to land with only 25 deg. Why? I don't know, but when I flew solo I found it much easier to control the landings with full flap. Its been my experience that if you fly a PA28 taper wing at the POH speeds and use the appropriate amount of flap (usually full), then it pretty much lands itself - all you have to do is be prepared to puuuuulllll the yoke back during the flare ;) |
I've never known anyone being taught that the Vref varies with loading.
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My Instructor was making the comment that, I and other pilots seem to be concerned about "slow flying", He said "you appear to be worried about this", and he was right.
I think it was the fact that some of us being taught over the last few years in PA28s and 172s have never done anything other than level flying. I have never been in a spin, let alone been upsidedown. Perhaps I should go on an advanced flying course, if there is such a thing. At least I now know that a PA28 160 will still fly at 55 knots, 2 up and half fuel. Ken |
I had a conversation with an instructor friend yesterday about airspeed.
He was concerned that this thread will have pilots going out and flying too slow, I ask him his reason for this PA28 / 75 knot approach speed and this use of only 2 stages of flap for landing. His reply was "thats what I was told this on the instructor course", and that many pilots would not be able to judge when to raise flap during a go-around. This seems to be a "new"(over the last five years or so) instructor thing. May I suggest that we have people with PPLs, who should not have them, as they have never really learned to fly. If this is the level of the "new instructors" we now have, where are we going with flight trainning?? Tony |
many pilots would not be able to judge when to raise flap during a go-around |
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