Landing at less than book numbers...

EdFred

EdFred

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...I mean well less.
Book says 76mph ~ Vso X 1.3
I come in at like Vso x 1.15 or less. - and with only 2 notches of flaps. (25º)

I know everyone says "fly the book, fly the book, fly the book," but coming in at book numbers it's lotsa float, and lotsa runway usage. I don't touch the yoke (at least in pitch) until I'm over the numbers, and keep the right hand on the throttle all the way in. Any major issues with this?
 
N2212R said:
... Any major issues with this?
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Dunno. Book #'s for our club 172 is 65kts, I like 50-55kts over the fence empty. Nice short tidy landings, less float and balloon.
 
I would think you are OK, as long as you are on top of things. Two things to think about are: 1) the Vso number probably doesn't exactly equate to two notches of flaps, and 2) you are probably underweight and therefore have a slower stall speed.

N2212R said:
...I mean well less.
Book says 76mph ~ Vso X 1.3
I come in at like Vso x 1.15 or less. - and with only 2 notches of flaps. (25º)

I know everyone says "fly the book, fly the book, fly the book," but coming in at book numbers it's lotsa float, and lotsa runway usage. I don't touch the yoke (at least in pitch) until I'm over the numbers, and keep the right hand on the throttle all the way in. Any major issues with this?
Click to expand...
 
N2212R said:
...I mean well less.
Book says 76mph ~ Vso X 1.3
I come in at like Vso x 1.15 or less. - and with only 2 notches of flaps. (25º)

I know everyone says "fly the book, fly the book, fly the book," but coming in at book numbers it's lotsa float, and lotsa runway usage. I don't touch the yoke (at least in pitch) until I'm over the numbers, and keep the right hand on the throttle all the way in. Any major issues with this?
Click to expand...

Why only 2 notches of flaps ?
 
Less flaps = less drag. You'll probably touch down early, but it may take just as long to slow down on the runway.

It may be highly dependant on the plane. I've always been told that in Piper Cherokees, the last notch of flaps provides mostly drag rather than mostly lift.
 
As in most answers, mine is "it depends". Most book numbers are calculated at full gross weight. If its just you in the plane, your 1.15 x Vso may be 1.30 x the real Vso adjusted for weight.

There are at least three factors in play here.

First Question - what is the true Vso. Carrying the weight you usually fly with, go out and fly straight and level with two notches of flaps, gradually reduce your speed in increments and see what the speed is that you stall at vs. the "book" Vso.

Second factor - how much cushion do you want over the true Vso? The cushion is for momentary inattention, wind changes, etc.

Third factor - the closer you are to Vso the mushier and less effective your control surfaces. I know that because of this reason Cherokee 6's are recommended to be at 1.4 x Vso.
 
Dave Krall CFII said:
Why only 2 notches of flaps ?
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Because that last notch of flaps just slams ya into the ground. It's all drag. The 2 notches of flaps makes it silky smooth.

As far as using more runway with the 2 notches - I'm still beating the numbers in the book.
 
N2212R said:
Because that last notch of flaps just slams ya into the ground. It's all drag. The 2 notches of flaps makes it silky smooth.

As far as using more runway with the 2 notches - I'm still beating the numbers in the book.
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If you're "getting slammed into the ground" by that last notch, it indicates probably flaring to high/too soon. Instantaneous, amplified control inputs to whatever extent are necessary will counteract mushiness associated with landing at slower, gear-saving speeds.

Full flaps do add a lot of drag but that's not a problem plus, they give a touch more lift, especially with the addition of 100 to 1000 RPM or more just at the right nanosecond to increase the slipstream cushion in ground effect.

The unique landing smoothness that then becomes possible, combined with the slight noise distraction to PAX by the addition of engine power, will mean they don't even hear the anticipated minor tire chip and won't even know the aircraft has actually landed until it's been rolling awhile.

The same results can be obtained without power as well but flare initiation time is even more critical and altitude measured in inches counts for that type of max performance result.
 
N2212R said:
...I mean well less.
Book says 76mph ~ Vso X 1.3
I come in at like Vso x 1.15 or less. - and with only 2 notches of flaps. (25º)

I know everyone says "fly the book, fly the book, fly the book," but coming in at book numbers it's lotsa float, and lotsa runway usage. I don't touch the yoke (at least in pitch) until I'm over the numbers, and keep the right hand on the throttle all the way in. Any major issues with this?
Click to expand...

Not enough info Ed. Is Vso=76/1.3 mph IAS or CAS? Is that for MGW? How steep is your approach?

The steeper the approach, the less float you'll have for a given IAS and weight (assuming you remove all power during the round out).

1.3 x Vso is intended to provide a sufficient margin over stall without carrying too much energy into the flare. It is usually assumed that you will reduce to 1.2 Vso as you cross the threshold and before enterring ground effect. To get an accurate number to use on the ASI, you must compensate for the difference between IAS and CAS as well as for your actual landing weight.

I think it's pretty much a given that you will use less runway if you make an approach at the "proper" airspeed and descent angle using full flaps vs partial.
 
MSmith said:
Less flaps = less drag. You'll probably touch down early, but it may take just as long to slow down on the runway.

It may be highly dependant on the plane. I've always been told that in Piper Cherokees, the last notch of flaps provides mostly drag rather than mostly lift.
Click to expand...
That be true of most piston singles and not just Cherokees. C-150, anymore than flaps 10 on the go after a T&G and you're probably not gonna' survive that first turn in the patt. Same with many others.
 
ah. I have a book on a 1972 Cherokee 180. CAS to IAS error with full flaps is +5 mph. So i you are indicating 65 mph, that means you are going 70. Which at full gross is more like 1.25 VSO. And I don't think with just you and even a lotta gear, that you get within 300 of gross. .93 squared would reduce Stall by another 13%, too :)
 
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