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Touch and go distance vs. landing/takeoff distance

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Touch and go distance vs. landing/takeoff distance

Old 27th May 2018, 10:56
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Question Touch and go distance vs. landing/takeoff distance

Hi gents, question time. Assume a short airfield with c.a. 3 meter-high obstacles at both ends. The calculated takeoff and landing distances for the actual conditions (obstacle clearence, weight, altitude, temperature, wind) are practically the same as the awailable runway length, so we should be able to fit, but barely.
Now in this case, is it safer OR more dangerous to make a touch-and-go on that field under the same conditions, instead of landing and taking off separately?
Initially I was under the impression that doing a touch and go must be safer, as we can easily accelerate and climb away, should something not look right.
But after doing this exercise, I am not so sure anymore
We touched down roughly at the intended distance from the threshold, but we had excess speed and bounced..
I added power, then it took precious seconds for the electric motor to move flaps from landing to takeoff position, and our initial cimb rate was half of what we usually get with takeoff flaps.
To play it safe, I had to manouver away from the obstacles ahead, as I wasn't 100% confident I would clear them in case of flying the normal runway heading.

Thanks for all insights.
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Old 27th May 2018, 11:32
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As a starter ,I would use a runway longer than` t/o distance plus landing distance x1.5` as a minimum,allowing you to re-trim and reset flaps,on the roll.
Otherwise ,you may just meet the fence
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Old 27th May 2018, 12:11
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If runway length available is a performance consideration, touch and go's are probably a poor choice. There is no performance data in the flight manual to support the decision to attempt a non standard maneuver (from the aircraft performance certification perspective), and there are too many variables in the execution of the maneuver. Consider it backward: Would you perform a standard takeoff on that same runway, with the intent of landing back from ten feet up? I will do that in my STOL C-150 on my 2100 foot runway, but would never consider it in my other aircraft.

Of course, flaps should be in the takeoff range for takeoff, but the risk of distraction, getting it wrong, fully retracting them unintentionally, or retracting the gear by mistake make reselecting the flaps a poor idea. Though I am an advocate for full flap landings as a norm, when doing intended touch and go's, for electric flap types, I would rather land with half flap, and takeoff that way, with the intention of reselecting the flaps when the climb is established, and things are settled in the cockpit. Remember that every certified type and electric flaps has demonstrated that a climb away of at least 200 FPM can be flown with full flaps. If you're depending on more than 200 FPM for a safe departure during routine training, you should not be attempting touch and go's!

I find that flying is more safe, when tasks are broken into their correct segments, with a built in opportunity for a pause and assessment in between them. It can be done while rolling on the runway, but runway length is used up quickly, and the pilot cannot completely pause and assess, because of the need to keep the aircraft safely on the runway. If I did not feel that I could comfortably include a count to 5 in between all the other things which had to happen in the cockpit between touch and go, I would not go. If using the performance charts of the flight manual comforts you, I would find the identifiable feature on the runway which represents the beginning of the specified takeoff distance for that aircraft in those conditions, and if, during your touch and go, you have not added full power for takeoff by passing that point, I would stay. If that was not enough runway length to stop on, then something was really wrong! Explaining that that is your intended go/no go decision criteria would probably look really good to insurer's and authorities, should they ever have cause to ask!
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Old 27th May 2018, 12:55
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rnzoli

Your speed should be correct and stable by let say at the latest 200ft on approach and if not then go around, your speed at the threshold must be confirmed as correct or go around. Forcing the aircraft onto the ground because you are too fast is pointless and is full of hazard as you experienced.

If you had decided to stop and not go around you may not have stopped before the end of the runway. Lift is a function of speed so if you are too fast the wings will be generating too much lift with poor friction with the ground, like being on ice, braking therefore may also be ineffective and could lead to a loss of control when applied.

Landing distances are calculated from 50ft above the threshold and at the later stages of the landing roll normal breaking (i.e. the brakes not slammed on) It is normally possible in light aircraft to touch down at the threshold at the correct speed.which offers a considerable benefit over the landing distance. The C152 POH informs that the landing distance is 1200ft (366m ) but the landing roll is 475ft (145m). The airborne part is approximately 40% of the whole distance. The PA28-161 gives a landing distance of 1135ft (346m) and the roll 625ft (191m) The airborne part being 55% of the overall distance.If you touch down too fast you will lose a large part of these benefits if not all of it.

Of course the above calculations will vary with density altitude, w/v and aircraft weight. Pilot DAR's contribution is excellent in my view.

Last edited by Fl1ingfrog; 27th May 2018 at 12:59. Reason: add info
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Old 27th May 2018, 14:47
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Thanks! A lot of good thoughts, much appreciated. .

Last edited by rnzoli; 27th May 2018 at 19:02.
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Old 27th May 2018, 19:33
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I should think that, if the runway length is only marginal, a touch-and-go can be limited to effectively "going" - full power, in other words - as soon as the wheels have "touched" ground; instead of slowing down to taxi speed before going again, as I learned standard practice? As a student, the hardest point is short final and flare, or so at least it was for me.

BTW I seem to remember LHTL is a former military airbase with a longish hard runway so you must be talking about another aerodrome?
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Old 27th May 2018, 20:43
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No, it's not LHTL, that's really long.
It's another private airfield with 410 m paved runway. It is owned by a former aerobatic pilot, so I thought if he can put his fast and powerful aircraft down there, I should be able to do that with my slow kite too :P
And yes, the plan was to touch down on main wheels and immediately power up, without even touching down on the nose wheel. I did that at another (longer) grass field earlier this year, and it was kind of cool
Now, as often does in aviation, something completely different happened, due to the narrow runway I got the illusion of being high.
So we experienced a mild, but still dangerous nose wheel touchdown first, with all the porpoising effect that followed. I just tried and of course, couldn't arrest the second touchdown (albeit on main wheel first this time), and powered up from there, kept it airborne in ground effect, got the flaps to T/O, checked RPM selector etc. Still, speed was not really increasing yet, so I was afraid of pulling too agressively, but a tree ahead grew uncomfortably big, so I decided to turn slightly.
(I have got the sequence on video, not for public use, but if you're interested, send me a PM and willl send you the link to it.)
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Old 28th May 2018, 00:44
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without even touching down on the nose wheel.
Is an excellent exercise in control, though not beneficial, if it becomes so distracting that the landing goes bad, and the nose wheel touches first. In my opinion, if the nose wheel touches without the aircraft weight being firmly planted on the main wheels, the landing was unsafe, and potentially damaging. If you can't hold the nosewheel off without going up, you're going way too fast to land. 410m is a short runway for most certified aircraft. Not impossible, but demands a very precise approach. A touch and go there is a poor idea, tree or not. A touch and go is a deliberate combination of a landing and a takeoff, you are demanding to very different tasks be executed back to back, which is not normally good, and "immediately" powering up to accomplish means that not enough allowance was left for reconfiguration of the aircraft and the pilot's task management. If 5 seconds of task transition time is not safely available, a touch and go is not safely possible.

Like "ground rush" during a dive recovery, "tree rush" is also a visual factor in departure. It's a problem, in that pilots tend to try to out fly the tree by a wide margin - it looks big and close. Aim to hit the tree about two thirds up. You won't hit the tree, because your sense of self preservation will demand that you pull up a bit at the last seconds. Clear the tree by a few feet at a safe flying speed, rather than clearing by a hundred feet at an unsafe slow speed. Demanding a 20 foot climb in the last seconds to clear a tree will work, ease it up, don't jerk it up, you've got some inertia, don't build up a whole bunch of drag by jerking the nose up, or dragging the plane up below Vy, or worse below Vx. It is possible to attempt to climb, but to create so much drag that the aircraft really does not climb. This is its own big topic, and I've been really scared a few times while right seat to a pilot who was caught in this trap. Allow the plane to accelerate to safe flying speed first, then climb it.
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Old 29th May 2018, 02:21
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Originally Posted by rnzoli View Post
We touched down roughly at the intended distance from the threshold, but we had excess speed and bounced..
I added power, then it took precious seconds for the electric motor to move flaps from landing to takeoff position, and our initial cimb rate was half of what we usually get with takeoff flaps.
To play it safe, I had to manouver away from the obstacles ahead, as I wasn't 100% confident I would clear them in case of flying the normal runway heading.

Thanks for all insights.
At the risk of being rude this description really made me cringe. POH landing distance is meaningless unless the approach is flown on speed and with the correct flight path. It would have been obvious at 100 feet AGL on final that the aircraft was going to fast and high on the approach path. The “touch” part of this touch and go was not going to work and the go part should have been been immediately carried out. Getting to the position where you have to do low level manoever is to avoid hitting the departure obstacles is how people kill themselves.

My criteria for a student on landing for every landing is + - 2 kts and no significant power or pitch change to fly to the planned touch down point with the touch down occurring in the correct tail low landing attitude touchdown; from 100 feet AGL to wheels down.

Make a point of striving for that all the time not just on the short runways and you will never get into the situation you described



Last edited by Big Pistons Forever; 29th May 2018 at 02:47.
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Old 29th May 2018, 09:06
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Touch and go or bounce and broken

First rule; You need plenty of space if this is the desired training regime so the exercise is not rushed. There are many fields where because of a lack of real runway length the student is thinking about the GO before he has even 'touched'. Todays training is far from ideal in many ways, and lacks continuity. I hear lots of stories about multiple instructor sorties, plus the slightly rushed situations due to lack of training airfields, and restrictions on 'circuits'. The initial training for a student is so important as this is the basis of his future foray into aviation, and should be a bedrock of GOOD PRACTICE, not rushed exercises. The modern day student has a lot to contend with and needs to be confident on the 'handling' side so he can cope with the much more congested airspace.UK weather, and increasing radio load. It is quite easy to 'speed up' once you have the basic skills, but not at all helpful trying to squeeze the system at the start. We all know that flying is an ongoing learning curve, but the first steps are all important and need SPACE of all sorts.
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Old 29th May 2018, 12:15
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Originally Posted by Big Pistons Forever View Post
At the risk of being rude
No worries, thanks for your feedback, no one here can be as rude as a huge tree branch hitting a wing on climb-out.

Originally Posted by Big Pistons Forever View Post
for every landing is + - 2 kts
Really? What about windhear, turbulence etc. As we normally practice on long runways, instructors on check rides expect us to approach +10-15 kts above minimum approach speed. Needless to say how tricky this becomes, when we fly to short airfields....
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Old 29th May 2018, 17:24
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From lots of experience at judging Model Flying T+G Competitions, I have seen many methods of doing a Touch and Go, especially if you are trying to do as many as possible in just a couple of minutes.

If you fly a correct landing, fully flaired, and land at Vs, then you need to accelerate back up to take-off speed before taking-off again and climbing away... All very time consuming. So most Model T+G Competitions are won by flying at Vapp, then bouncing on the Wheels, as you apply full power for the go-around and next T+G.
It' all in the title... Just a Touch is all that is needed. ( even with just one wheel.)

I have even seen model gliders with skids do T+Gs, but admittedly flown a lot faster than Vs. Also a full size glider at the Myndd, managed a touch before the Bungee launch point on the ridge..
.
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Old 29th May 2018, 22:30
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If you fly a correct landing, fully flaired, and land at Vs, then you need to accelerate back up to take-off speed before taking-off again and climbing away... All very time consuming
As the saying goes, if you think safety is time consuming, try an accident! Fly the aircraft in accordance with the procedures and performance information in the flight manual. That very certainly will not include:

by flying at Vapp, then bouncing on the Wheels, as you apply full power for the go-around
instructors on check rides expect us to approach +10-15 kts above minimum approach speed.
The aircraft manufacturer has stated an approach speed range in the flight manual. The aircraft should be flown in that speed range. Doing otherwise could raise questions, should one go off the far end of the runway....
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Old 30th May 2018, 20:29
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Short runway with a tall tree at the end? hmm. Even an experienced pilot might get in trouble, much better to STOP under control, and taxi back to the beginning.

In Texas, the runway was plenty long, except a couple of deer decided to canter across,,, Narrowly avoided the livestock, and couldn't blame the farmer.

And on my annual check ride, in my Supercub (used mainly for towing up gliders at Shenington in those days), the very experienced instructor as we turned back toward the airfield over Banbury, pulled back the power about half way, and said, now what are you going to do about that? Of course I was not permitted to increase power. However, as we gently descended on track, and the wind was not too strong, I did not even try to do a circuit. Just came carefully straight in downwind and landed. There was no other active traffic, so that worked quite nicely, and I was quite smug about surprising the instructor, who thought I would go for a standard into wind circuit and end up horribly low!
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Old 30th May 2018, 22:27
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rnzoli you say: ".......instructors on check rides expect us to approach +10-15 kts above minimum approach speed". I have never heard of a "minimum approach speed", you may mean by this the recommended Minimum Safe Approach Speed. This is normally considered to be the scheduled speed at the stall for the approach plus 30%. For most light training aircraft 30% would be something like the 10-15kts you mention. Plus 30% is plenty to meet the unforeseen. If you intend to land then increasing the speed is never the correct choice whatever the conditions.
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Old 2nd Jun 2018, 16:17
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From my experience touch and go manoeuvres are generalyy under performed and not practised enough by qualified pilots. Therefore when eventually they do one it comes as a bit of a shock to the system. Similar to go arounds where the vast majority of pilots make a pigs ear of it. IMO a short grass strip, with obstacles at either end, is fine if experienced,, current and flying a Cub, or similar, where you understand the aeroplane, its capability in line with POH, and can be pulled up in a dime if it all goes wrong. There are a number of accidents in the go around/Touch and Go regime every year where evidently pilots did not understand the operational limits and capability's of their machines. I would prefer to go and practice on a large open runway, understand the performance parameters and introduce the shorter fields when really confident. Forgive me if you are at this stage, but please do not underestimate the manoeuvre.
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Old 2nd Jun 2018, 20:20
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Yeah, well.... I am not sure what stage I am in, maybe this is the problem after all.
In 2015, I practiced for precision landing competition (I did not compete though).
In 2016, I landed on a 500 m runway, high and hot (warm), nearly overrun into the safety area.
In 2018, I made this touch-and-go on 400 m runway, and had to manover some trees out of the way on the departure end.


Mmmmm..... I think I can see a dangerous tendency here!

By the way, someone made a video clip about the very same airfield a few years back. There is a small stream at the departure end and the runway elevation slopes downwards.
But the trees growing there are pretty big, I didn't expect THAT.

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Old 2nd Jun 2018, 23:15
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Originally Posted by rnzoli View Post
Yeah, well.... I am not sure what stage I am in
I know what stage I'm in - most of my flying has been from 2km of tarmac.

Before going to a (comparatively) much shorter grass runway I would usually fly an hour of circuits (full stop and backtrack) on grass a few days beforehand, because I know I'm not usually in practice. And if by the end of the hour I wasn't consistently stopping by my chosen mark I'd rethink the trip to the short runway.

What I've never thought to practice is deliberately coming in 5kt too fast and then going around after the first bounce ... so this has been an "interesting" discussion.
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Old 3rd Jun 2018, 07:53
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The.1.5 x runway lenght or the 5 seconds separation between touch-down and the "go" are really interesting and useful thumb rules that I learnt here.
I also see now, that small fields need full circuits and at least one low-pass to discover all obstacles, to get used to the local turbulence/windshear characteristics, to get familiar with visual decision points along the runway. A stabilized straight-in approach is not safe enough, too little time to absorb all necessary details for a very short runway and time/distance runs out way faster than usual.

It's also a great idea to practice this in advance, but there may be times, when this knowledge will be necessary without the chance to practice in advance. There has to be a way to make sure that you can land or go-around with uncomprimised safety, even when the lenght is the shortest possible in the POH or AFM. If this capability requires 1 hour prior training, it's also a subtle risk (although much smaller than going somewhere totally unprepared).
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Old 3rd Jun 2018, 12:26
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Practice is vital. Where to practice can suddenly become very important too! For "non standard" flying, which certainly includes touch and goes, practice on a runway you know well. If this means flying a number of normal circuits there first, then do more aggressive flying if you're comfortable. Get to know the hazards, and visual cues there. And in choosing the place, choose a place where help is nearby if it goes bad! If you get it all wrong, and end up in the tree off the end of the runway, you'll very much appreciate if that tree is along the perimeter of a busy airport, with emergency services, and an access road nearby, rather than a long way from anywhere, un noticed.

On one of my trips to the Canadian arctic, I planned a one day camping trip onward from the group. I informed them in great detail where I would go, and I carried a SPOT, and a sat phone. I chose my camping lake with a beautiful beach and waterfall - it was 93 miles away from anyone. I remember reminding myself that was very much NOT the place to horse around in the plane, everything calm and cautious. No problems. That contrasted with a Youtube cockpit video clip I had seen of a private flying boat landing in a magnificent fjord in Greenland, with some extreme water maneuvering once down. Well unless that pilot was being followed there by a fully equipped SAR team, that was a dumb place to do that! It seemed to work out okay, but what a risk!

So last summer, when it all went wrong, the pilot I was training, and I ended up being ejected through the windshield, and floating by our torn lifejackets, grasping bits of a sinking plane. Happily, the place I'd chosen for this training was a water aerodrome very well known to me, right next to a busy airport, where everyone knew me, and served by the fire department for which I'd been a volunteer for 25 years. The crash was witnessed, and we were rescued within minutes. The people who got me from the water to the hospital all knew me, and my wife was so well informed, that she was waiting at the hospital when I arrived. My casual choice as to where to train most certainly saved my life, and that of my fellow pilot - and the uninsured wreck could be taken out by crane at the dock, rather than having to hire a helicopter.

The freedom of flying imposes a responsibility to make your own decisions in the interest of greatest safety. Yes, we must practice emergencies, and non standard techniques, do it at a place at which a problem does not become instantly worse because of remoteness. So my first three practice forced approaches onto the water yesterday were in the same lake, and, this time, instead of leaving the lake by ambulance, I left in the airplane I'd arrived in!
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