Landing at Duncan

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CpnCrunch
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Landing at Duncan

Post by CpnCrunch »

(moving this from the accident thread)
Cat Driver wrote: If you can not touch down on the first couple of hundred feet of runway go get some more training because you should not be instructing.
Does that not mean you'll be flaring before the threshold, i.e. in the drop-off that usually has downdrafts?
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Re: Landing at Duncan

Post by Cat Driver »

What would cause a downdraft at the start of a runway and would there be any indication that a downdraft may be expected?

I stated a couple of hundred feet inside the threshold not the first inch.

How far do you float after a flare on a short runway?
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Re: Landing at Duncan

Post by CpnCrunch »

Cat Driver wrote:What would cause a downdraft at the start of a runway
The terrain generally causes downdrafts there, for obvious reasons. And it's *before* the start of the runway we're talking about, not at the start.
How far do you float after a flare on a short runway?
I'm not sure, but probably more than 100ft in a 172 @ 2200lb.

My point is: if you start flaring in the dropoff before the runway, how do you prevent hitting the cliff if there's a downdraft? It seems that you're likely to end up like this guy:

viewtopic.php?f=118&t=104074

What possible advantage is there to landing in the first couple of hundred feet?
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Re: Landing at Duncan

Post by Cat Driver »

The terrain generally causes downdrafts there, for obvious reasons. And it's *before* the start of the runway we're talking about, not at the start.
Where did I say I flare " before " the start of the runway?
I'm not sure, but probably more than 100ft in a 172 @ 2200lb.
I allowed a couple of hundred feet not one hundred feet.
My point is: if you start flaring in the dropoff before the runway, how do you prevent hitting the cliff if there's a downdraft? It seems that you're likely to end up like this guy:
And I did not say flare in the drop off before the runway.
What possible advantage is there to landing in the first couple of hundred feet.
Well I always want runway ahead of me I don't need, rather than runway ahead of of me I may need.

What disadvantage is there to landing in the first couple of hindered feet?
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photofly
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Re: Landing at Duncan

Post by photofly »

I'm not sure, but probably more than 100ft in a 172 @ 2200lb.
I'm not sure the weight has much to do with it, if you adjust your approach speed for your landing weight (I do recall being pilloried here a couple of years ago for the suggestion that pilots might think about doing that in a 172). If you don't adjust your approach speed in consideration of your landing weight, you'll float further the lighter you are. But then if you're keen on precision landings, you would have adjusted your approach speed appropriately.

I do like the older 172s with 40 degrees of flaps, for short landings. I think they rather spoiled the aircraft when they limited the flaps to 30.
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Re: Landing at Duncan

Post by FishermanIvan »

When I flew into Duncan, I didn't do touch and goes. I backtracked, and took off.
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Re: Landing at Duncan

Post by Cat Driver »

Lets look at the advantage of landing in two hundred feet or less.

I flew C117's based in Nanaimo.

My hangar was at the south end of the airport and if I was landing on runway 34 I would turn off at the taxiway about half way down the runway on the left.

If I were to touch down at the displaced threshold I would have to use a fair amount of braking to turn off at the taxiway.

Conversely if I touched down in the first hundred feet or less the need for braking was really no big deal especially in an empty airplane.
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CpnCrunch
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Re: Landing at Duncan

Post by CpnCrunch »

Cat Driver wrote:
Where did I say I flare " before " the start of the runway?
I did, in my initial post on the subject. I assumed you'd need to start flaring before the start of the runway.
I allowed a couple of hundred feet not one hundred feet.
So how long exactly would your float be in a 172 @ 2200lb, assuming you've had to adjust power and increase airspeed due to downdrafts on short final, and you've only 30 degrees of flap?

What disadvantage is there to landing in the first couple of hindered feet?
The risk of touching down before the runway. That seems a much higher risk than landing 300ft or 400ft down the runway, which is perfectly safe at Duncan.
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Re: Landing at Duncan

Post by Cat Driver »

I can only speak for myself.

I flew airplanes for a living and thousands of hours of my flying were off airport flying, mostly in DC3's and Twin Otters.

In over five thousand hours of flying those airplanes I " NEVER EVER " landed short of a runway or ran off the end either.
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CpnCrunch
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Re: Landing at Duncan

Post by CpnCrunch »

Cat Driver wrote:I can only speak for myself.

I flew airplanes for a living and thousands of hours of my flying were off airport flying, mostly in DC3's and Twin Otters.

In over five thousand hours of flying those airplanes I " NEVER EVER " landed short of a runway or ran off the end either.
Neither have I. So how far do you float during a short field landing in a 172? And have you landed at Duncan since the length was reduced to 1500ft?
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Re: Landing at Duncan

Post by Cat Driver »

I haven't flown a 172 for over twenty five years, and same goes for flying into Duncan.

Anyhow Crunch this conversation is going nowhere mostly because we are galaxies apart in how we fly and how we think about flying.

So I am going to let someone else give their opinions and I will just read instead of post.

I do think that I remember landing a 172 in a couple of hundred feet with a bit of wind and touching down right at the start of the runway on a few occasions....but that was a long time ago so maybe my memory is a bit blurred.

Maybe one of the guys that teach on them can comment on how short you can land a 172.
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Re: Landing at Duncan

Post by CpnCrunch »

Cat Driver wrote:I do think that I remember landing a 172 in a couple of hundred feet with a bit of wind and touching down right at the start of the runway on a few occasions
Well, it's pretty easy doing that at Nanaimo, as there is a big flat bit of grass before the start of the runway (unlike Duncan which has a big cliff). A stiff headwind will also help.
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Re: Landing at Duncan

Post by CpnCrunch »

photofly wrote:
I'm not sure, but probably more than 100ft in a 172 @ 2200lb.
I'm not sure the weight has much to do with it, if you adjust your approach speed for your landing weight (I do recall being pilloried here a couple of years ago for the suggestion that pilots might think about doing that in a 172). If you don't adjust your approach speed in consideration of your landing weight, you'll float further the lighter you are. But then if you're keen on precision landings, you would have adjusted your approach speed appropriately.

I do like the older 172s with 40 degrees of flaps, for short landings. I think they rather spoiled the aircraft when they limited the flaps to 30.
Well considering the stall speed varies by 15mph in a 172 depending on how it's loaded, that will make a difference to the minimum speed you can use.

I did a search for float time vs speed in a 172, but can't find anything useful. What would you estimate your flare/float time would be during a short field landing with 30 degrees of flap at mid weight?
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Re: Landing at Duncan

Post by photofly »

Honestly, you can make it as long or as short as you like.
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Re: Landing at Duncan

Post by CpnCrunch »

photofly wrote:Honestly, you can make it as long or as short as you like.
So, can you find a video of someone doing it in 100ft (without using power)? I can't find any. Ex:

https://www.youtube.com/watch?v=Ebwvpw4ZpEs
https://www.youtube.com/watch?v=Zx2rjCd998s

First one lands right at the start of the runway, but has a very long hold-off (dragging it in with power just above the stall). Second one is a more normal short-field landing, but still has a 3-4 second (300ft) flare.

Even this "ultra short field landing" holds it off for 4 seconds (I think it's just the wind that makes it "ultra short"):

https://www.youtube.com/watch?v=SnXPt3lkwuw
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Re: Landing at Duncan

Post by BeaverDreamer »

Probably no point in arguing this but if you can't keep your flares under 200 feet in a 172 while doing short field landings you shouldn't have any business operating out of short fields... in my non-expert opinion.
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Re: Landing at Duncan

Post by photofly »

So, can you find a video of someone doing it in 100ft (without using power)?
Why are you worried about the use of power?
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Re: Landing at Duncan

Post by CpnCrunch »

photofly wrote:
So, can you find a video of someone doing it in 100ft (without using power)?
Why are you worried about the use of power?
I meant, not using power to drag it in horizontally.

So, can you give me numbers for approach speed and flare distance? I'm pretty sure if you use the book speed of 61kts with 30 degrees of flap you'll float about 300ft, but I could be wrong. Using much less than that doesn't seem like a great idea if you're landing somewhere with downdrafts and a cliff on short final and the windsocks pointing in different directions, but again I could be wrong.
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Re: Landing at Duncan

Post by Schooner69A »

I haven't flown a -172 for some time, but it seems to me that the listed book speed of 61 knots is too fast if you're contemplating a short field landing. That may be what the book says, but you're nearly twenty knots over the stall. That's a lot of energy to dissipate.

If you're proficient on the aircraft, I'll bet you could shave 5-7 knots off the approach speed, start the flare short of the runway, and greatly minimize the resulting ground run.

In my RV, stall is around 50 knots, and a normal approach sees me initiating the flare with about 5-8 knots to play with... I could better it I'm sure, but the approach used 90% of the time has trees just short of the runway forcing a "dump" if you want to put it on near the button.

The previous comment about restricting the available flap on the 172 is right on. I'd like to have another 10 degrees on my aircraft - forty isn't nearly enough drag on those things! (;>0)
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Re: Landing at Duncan

Post by photofly »

For the 172S:

The calibrated Vso is 48 knots at 2550lbs. 1.3Vso is 62.4KCAS corresponding to a shade over 60 knots indicated. I guess they rounded up. That gives you a margin against the stall of 14 knots. Not 20.

Basic CPL level task: calculate an appropriate approach speed for a different weight, using the formula in the flight test guide.

Here's a sample calculation for an appropriate approach speed for a C172S landing at 2000lbs:
New approach speed is sqrt(2000/2550)*1.3*48 = 55KCAS which corresponds to 49KIAS. Call it 50 knots to make a round number.

300lbs in the front seats and half tanks puts you at 2130lbs in a 172S I fly. Approach speed works out at 51KIAS, if you want a short float.
Using much less than that doesn't seem like a great idea if you're landing somewhere with downdrafts and a cliff on short final and the windsocks pointing in different directions, but again I could be wrong.
It's up to the pilot to manoeuvre the airplane safely in all phases of flight. Different pilots with different skill levels and different levels of local experience can and should make different decisions about what they can safely achieve. Pilot A can very reasonably decide that touch and goes at a particular airport aren't safe for them, while pilot B correctly comes to the opposite decision. For this airport it sounds like it's a pilot skill issue and not an airplane capability limitation of the 172 that would determine things.
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