I do most of my flying from strips that are sloping / undulating. There are several factors to take into account.

First, preparation. Know what the slope / undulations are before you arrive. As a general rule, if you can see the slope from the air, it is quite steep. The undulations will probably therefore only become apparent when you're low, and you may not be in a position to land on the most favourable part of the strip.

Second, precision. This has been stressed by several people above. You need to choose your touchdown point, and make sure you touch down on it.:) The best way to do this is to pick an aiming point a suitable distance before your touchdown point (the distance depends on the wind, the aircraft type, the slope, and the speed at which you have decided to fly the approach), and fly a constant-speed approach to that aiming point. You don't need low-speed back-of-the-drag-curve heroics. If the strip is short as well as undulating, you just move your aiming point a suitable distance before the strip to ensure you touch down right at the start.

Third, the flare. Chuck Ellsworth detailed this far better than I can recently. As gasax says, on an undulating / sloping strip there's no point in looking at the end of the strip, 'cos you often can't see it. An important point about the flare on a sloping strip is that it should be initiated at the normal height above your touchdown point. This could mean that you are much higher than normal above the ground when you initiate the flare. You have to resist the urge to fly down to the normal height then pull up sharply to flare, or you will likely stall. It takes a bit of practice to get used to it, but is not a big deal.

Fourth, speed. The rule of thumb I use is as follows: normal approach speed for any slope up to 10%. Add 1km/h (one day the French will use knots for light aircraft... :rolleyes: ) per additional % of slope after that. So for a 20% slope, my approach is 10km/h (about 5 knots) faster than usual.

Fifth, power. Landing on a sloping strip, gasax's advice is spot on. If you cut the power to idle as you start the flare, and then have to pitch up significantly to get a 3-point attitude above the slope, your speed will fall very quickly and you will probably have a very abrupt arrival some way short of your intended touchdown point. If instead, you leave a bit of power on during the flare you can reach the 3-point attitude (do you say 2-point in a Europa :confused: )just above the touchdown point. Cut the power and you're down.

As a final comment, if you are able to choose your touchdown point I find it's generally preferable to land in the slope on an undulating runway. If you land in a "concave" section where the slope starts, the flare is more difficult - your pitch attitude needs to be continuously increasing to follow the slope. Landing in a "convex" section is harder still (but very satisfying if you get it right:cool: ). After the flare you need to relax the back pressure and follow the ground as the slope levels off. If you don't, you stall in from several feet up.... :uhoh:

I am a novice, but trained at Elstree.

Landed on 26 for the first time in 8 months yesterday and there was a little balloon-ette. Thinking about it, and your post, I think there is a greater tendency to do this on 26 and to land flat on 08. It's tempting to overreact to the slope.

Also, I was told to look at the end of the runway when I learned, and found it didn't help at all. Maybe I've developed a technique where I look ahead, but ignore the slope (if successful)?

I don't understand why you need to come in faster for a runway with a 'surge' - can someone explain? (But then I've missed a bit of this thread I think and have to come back from lunch now... :rolleyes: ) I find wherever I'm landing it's easier if my airspeed is on the lower side towards the end. Surely that's universal? Power sometimes helps me control sink rate too, again, dunno if this has anything to do with undulating runways or not.

Nice try Dude - but wrong. My objection to baby airline pilots is light aircraft pilots who fly approaches at 3 degrees using PAPIS and the like. This is not the way to operate light aircraft.

As for adding extra speed I only stated that for power off approaches to steep slopes - do try to keep up!

Anyone flying a 3 degree approach is likely in a nosedragger to bounce or wheel barrow on an undulating runway. The aircraft simply has too much energy (speed!) to stop flying. Try that in a taildragger and you will get a huge balloon. To achieve a genuine holdoff in ground effect you will not be flying a Vs +30% - there is every likelihood you will be around Vs.

If you fly a steeper approach, or you achieve a genuine holdoff rather than just 'flying onto the ground' you are flying on 'the back of the drag curve' - whether you like to think about it as that or not. The genuine hold off however consumes a lot of runway, because the 3 degree approach gives you such a speed margin to start with. You are perfectly correct that adding power from that sort of aproach just increases the length of runway - it does - but if you are flying over a large concave area that is exactly what you need - otherwise the sink rate will push the wheels up through the wing/fuselage/whatever.

In the flare (a proper flare that is), the aircraft has much less power than it needs, the speed is decaying rapidly, landing is imminent, if not beaten by a stall. Now all this happens very close to the ground so you don't stall - but many do sink very rapidly!

Aerobatic has filled in the details nicely.

The summary is that adding speed on uneven surfaces adds complication and danger, fly the attitude use the engine and control your landing point.

Sorry for ranting, but landing fast is actually an oxymoron.

Pardon me for my agricultural attitude to all this but for what it's worth heres my sixpenneth........

Questions I ask when going into an unfamiliar farm-strip. (I have yet to land at a tarmac strip that requires any massively different handling technique to normal, even the ones that do look lumpy like Elstree etc)

1. Are the bumps coming straight at you or are they slanted across the r/way? This does make a huge difference in terms of what to expect in the event of a balloon or even once you are rolling to a stop.

2. Are you landing into a x-wind where a ballooning episode could send things fruit shaped el-pronto?

3. What is the landing speed of the a/c? A Thruster is hardly going to be as affected by a lump at 30 kts as, say, a fast and floaty 182 with no passengers.

4. Is the last 150 m UPhill or DOWNhill. I recall landing away from the buildings at Eggesford once on a warm balmy day with no wind........anyone who knows it will understand what I mean.
:ooh: :ooh:

I do feel that if you try and judge the peaks and troughs then it is bound not to help really, the key is putting it down where you want it (normally about 30 yds behind where it ends up!!!)

Being too transfixed on the bumps only drags attention away from the rest of the job at hand such as flaring, keeping straight and watching the end of the runway coming at you.

I'll never forget going into Westbury-Sub-Mendip a couple of years ago and being so transfixed by the fact that the runway was curved that I almost forgot where I was aiming for, the plane gobbled up the runway faster than I would have liked.

The moments between travelling downhill and uphill always seem to slow the a/c down beautifully. I have always felt this is due to the "compression" factor in the u/c that takes out some of the momentum. You can feel it through the seat and this is the point I would normally apply the brake (if needed). Braking downhill (unless really necessary) never really seems that effective.

All the above relates only to particularly lumpy grass strips, perhaps not exactly where this thread was coming from originally?

IMHO I would say that taking off on strips such as those I am describing takes as much (if not more) concentration than landing.

On a day like that, if you don't touch down here in the Easterly direction BEFORE the first hump you're in trouble, or rather you're not, as long as you go around straight away.

Watched several go-arounds the other day by someone in a high performance aircraft, clearly spooked by poor visibility and rain, coming in hot and high, touching down after the hump and thankfully deciding not to brake downhill on wet grass.

On the other hand, touch down before the first hump and you have to put on lots of power to taxy up it. Undulating fields can work for or against you.

QDM

QDM, how's things in sunny Devon? Haven't been down to Eggeford for a year now but would like to call in one day soon.

Am I right in thinking that you lucky chaps who are based there must have some fantastic afternoons watching the antics that go on with first timers at that weird and wonderful strip? I can picture it now; barby smoking, beers flowing and........hey look lads here comes another one.........wahaaaaaayyyyyyyyyy!!!

Saying that, I find the flight down to you more stressful than a night in with the mother-in-law knowing my humble efforts at landing are going to be witnessed !!!!

Will drop in soon as have a friend at N. Tawton who I havent seen for over 12 months.

You've even got a new one-way strip at North Tawton now:

http://www.devonstrut.co.uk/tawmill.htm

Head south with the cheese factory on your left and you're on final. The owner is a gem and the strip is very good, although the grass is too long for the next week or so until he has silaged.

Most people here are pretty charitable and actually very few come in who aren't up to it -- they just take a look and go elsewhere, not that it's really very difficult. Now, how about doing it at night...?! ;)

See you soon. We're having a number of fly-ins over the summer and they're usually well-attended.

QDM

This topic is very interesting, and I wonder if someone could answer a q I have about undulating strip landings?

Is it common practice to retract flap in the flare to allow the aircraft to settle to the ground more quickly if for some reason the aircraft floats further than expected (ie due wind gust etc)?

thanks,
O8

Never heard of that technique. Wouldn't really want to try it either. If trying to make it "stick" last thing I would consider doing is retracting the flaps. My reasoning, the last stage of flaps are the "draggiest". I don't want to reduce the drag (any more than ground effect already has).

Any way, knowing my luck I'd retract the gear and not the flaps. Still, it would be a ripper of a short field landing. :D

I have never heard of dumping the flap in the flare.

At low speed you would drop like a brick with the nose dropping.

I have been taught though to dump flap after all the wheels on the deck to to stop gusts getting you up again, and to give the wheels more grip. Manual lever flaps lend themselves to this but electric take a bit more time.

If you want undulating runway try Barra it changes every time the tide comes in. Landing wasn't to bad just drop it on the top of a rise. Takeoff the sand sucks you down so when you do unstick you feel as if you leap into the air.

MJ

I've also heard of dumping the flaps only after you're firmly on the ground. Less lift means more weight on the tyres which makes the brakes more effective so you stop quicker, or so the theory goes. Can't say I've ever tried it though. And when the flaps and gear are on the same lever, as they are in my 'plane, it's not an option at all :eek: :D

I can see how, in theory, it may help with a short field landing, but I can't see how it's going to help with dips and crests, though?

FFF
-------------

It's never a dull moment here is it? People who cannot land on something not perfectly flat and now interesting 'advanced techniques'

I've heard of it but to be blunt think it's rubbish. The time period where flaps will give you enough lift to soar skyward after you have touched down is extremely short (so long of course as you didn't fly onto the runway at 1.3 x Vs!!!).

Of course there is the small matter of not retracting the gear inadvertantly, or seeing out of the windscreen to reach the flap lever, whilst you are still travelling quite fast.

Try actually holding the nose wheel off and the flaps will act as very effective airbrakes. On my Terrier (a taildragger) they are more effective than any brakes when in the full position.

Landing at the lowest sensible speed is going to be a far better bet than trying to stop 'lift' to enable better braking etc..

I agree gasax.

I was trying to figure out what O8 was meaning.

MJ

Thanks for the replies everyone - I appreciate your time.

To clarify, I was not referring to the practice of retracting flap when already on the ground, but retracting flap in the air in order to get on the ground earlier. Not that it makes much difference if you use the gear lever by mistake!

Somebody mentioned Nayland......

It's actually in Suffolk, and is remarkably free from undulations, just a steadily increasing upslope until you reach the crest of the hill, where it flattens out for about 150m. Wonderful strip, not for the faint hearted PPL fresh from GFT....

Normal take off is downhill, landings uphill no matter what the windspeed/direction is, but I have launched a Cub into wind from the 150m flat bit at the top.

I've spent the past 10 years trying to work out how a pilot (believed to be 'an instructor'), in a 150hp Super Cub (almost the world's best STOL aeroplane), managed to leave the aircraft in rather a mess in the upwind hedge????

Zlin

That deserves some kind of aviation achievement award. A little under gross, with a little wind down the runway, a 150Hp Super Cub is off in under 50 yards.

Interestingly, even though (perhaps because) it is such a benign low speed aircraft, many cub pilots die by stall / spin accidents. The chapter by Leighton Collins at the end of 'Stick and Rudder' gives a brilliant and chilling explanation of how such events come about. It should be compulsory reading and has certainly scared me off steep turns at low level (not that I needed much scaring).

David

Zlin526, Thanks for correcting my rather poor geography - thats why I put the question mark in after Essex. Hope I've not insulted anyone in either county!
Your description of Nayland is spot-on but I should point-out to anyone who hasn't been there that the "upslope" at Nayland is the steepest I know of anywhere in the UK. (Waits to be corrected)
I've always managed to get airborne before the start of the downslope but I've often wondered what it feels like to go over the "edge" while still on the ground.

QNH,

North Essex/South Suffolk tends to merge anyway..Its only just in Suffolk.

I've heard of (but not seen) a Prentice being flown out from Nayland! Not the worlds best performer in the R.O.C dept, as I'm sure anyone who's flown one will agree. Which makes me wonder how far down the hill he was before the wheels left the ground.

I was 'Lucky' enough to have logged 40 mins in one once, and was convinced we only got airborne cos the Earths curvature effect, and because we had a concrete runway! How the RAF ever accepted it into service will always amaze me.

A wonderful place is Nayland, and all credit to Tony Harris for keeping it special!

Ever try Wick?

Undulating slope, bumps and potholes that you really need to go round! And thats just on the main concrete slab...

Fun really

Bear555

I used Elstree for a number of years flying a slippery aeroplane. The tricks as I remember on 26, or 27 as it may have been then, are to anticipate a downdraught into the pan, having stayed high enough for comfort over the turbulance over the trees, then while anticipating the downdraught, head for a roundout in the pan and a touch down on the line, hopefully being able to turn off at the intersection, but more often than not having to backtrack.

Coming in from the west using the rough bit to flare, again getting the aircraft ready to touch down shortly after the runway proper starts.