Engine out on approach – would YOU make the runway?

[FlyingMonkey]

Andy,

If 40 doesn't give you any slower speed how will using 40 minimize landing energy?

 

It doesn't by much.  There is probably some small difference, a knot or two.  Not enough to be worth the trouble in normal landings, but in an off airport situation every tiny bit helps.  

[FlyingMonkey]

We do use 30°, for me it is because 40° runs out of energy too fast.

 

Reflex = cruise

zero = intermediate setting

15 = take-off

30 = landing

40 = special use like steep descent or short/short field or imminent crash

 

 

Exactly what I found, 40° just stops flying too abruptly.  I use the various flap settings exactly as you state.  

 

I also use 0° as my "pattern" setting.  At -6 the airplane gets faster than I want to be in the pattern.  I usually drop just under 100kt and go to 0° when approaching the airport a few miles out.  That makes it take a little longer to get into the pattern, but give me more time to assess what's going on at the airport and look for traffic.  The slippery CT is hard to get below 90kt on downwind at -6° unless you drop to ridiculously low RPM.

[FredG]

Tom, I am not trying to convince you (or anyone else) to use any particular flap setting when landing your airplane.

 

But, based on your recommendation to use the airplane AOI for guidance on such matters, I looked in my CTSW AOI for recommended flap settings for landing.  As I noted in my comments above, the AOI in my possession did not confirm your statements about FD recommended flap settings when landing the CT.  

 

I realize that you later clarified that your comments were in reference to the CTLS that you use for instruction.  I guess one lesson here is that we stop calling the CTSW and the CTLS by the same name ("CT"). 

[ralarcon]

Different strokes for different folks. What was the old saying ?" Any landing you can walk away from is a good landing !" . I would add, expensive but acceptable. I guess if it gets you down safely, its good. "Take offs are optional but landings are mandatory", sort of thing. I have landed acceptably well at all flap settings on my aircraft, with no damage. (CTLS)

 

Cheers

[gbigs]

Anyone arguing that 30 or 40 flaps does not increase drag by SUBSTANTIAL amounts and there for cut speed either hasn't tried it, or their flaps are out of calibration.

 

Again, 15 @ 62kts over the numbers is the standard landing config for the CT.   Zero flap landings are easily done also, just takes more runway.

[WmInce]

Exactly what I found, 40° just stops flying too abruptly.  I use the various flap settings exactly as you state.  

 

I also use 0° as my "pattern" setting.  At -6 the airplane gets faster than I want to be in the pattern.  I usually drop just under 100kt and go to 0° when approaching the airport a few miles out.  That makes it take a little longer to get into the pattern, but give me more time to assess what's going on at the airport and look for traffic.  The slippery CT is hard to get below 90kt on downwind at -6° unless you drop to ridiculously low RPM.

Concur with you Andy.

[FlyingMonkey]

Anyone arguing that 30 or 40 flaps does not increase drag by SUBSTANTIAL amounts and there for cut speed either hasn't tried it, or their flaps are out of calibration.

 

Again, 15 @ 62kts over the numbers is the standard landing config for the CT.   Zero flap landings are easily done also, just takes more runway.

 

That is *your* standard landing configuration.  I don't think you'll find that as a standard recommendation anywhere in the POH.

 

Of course 30° & 40° flap settings increase drag substantially...that's kind of the point.  They also generate substantial lift to offset the drag.  As long as you have either:

 

A ) A short enough distance to the runway, or; 

 

B ) A functioning engine

 

The excess drag is immaterial.  You are going to come in steeper and slower, and you are going to have less landing energy to dissipate on the runway.  This is *highly* desirable for a safety standpoint.  To compare, for approach you use 62kt @ 15° and in light winds I use 52kt @ 30°.  In energy terms at gross weight of 1320lb:

 

1320lb at 62kt = ~224,000 foot pounds of potential energy.

 

1320lb at 52kt = ~157,000 foot pounds of potential energy.

 

That's almost exactly a 30% difference.  We both have to get the airplane stopped (or nearly so) on the runway, so we each have to basically get that energy down to approximately zero, in the same distance.  You have a harder problem, because you have to get an extra 30% energy out of the airplane.  But you refuse to slow down, so that leaves exactly two ways to dissipate energy:

 

1) Distance

 

2) Friction

 

You can either land longer, allowing the airplane to float until the speed bleeds off (see, you still have to slow down!) to a point where the airplane will allow you to land it, or you can generate a lot of frictional heating.  In other words, plant the airplane as soon as possible and get on the brakes as hard as you safely can.  I still don't think you are going to be able to get that additional 30% of the total energy out in a similar distance, no matter how white-hot you make the brake discs...

 

But wait, there's more!  You said "15 @ 62 over the numbers"...so you are not slowing at all, all the way down.  If the wind is calm, I often let the speed come down as I get close to the runway (over the numbers, maybe 20-30ft high) , as low as 48kt.  In other terms, ~134,000 lb/ft of energy, or 40% (!) less than your plane has at the same point.  At that speed I only have to dissipate about 4-6kt to get the airplane to the stall (landing) speed of ~42kt.  At the same height, you have to burn off 20kt to get to the same speed.  You are not in contact with the ground to melt the brakes, so you have one option:  float.

 

Question:  How would you land on a short runway, say 1700-2000ft long? 

[Tom Baker]

Andy, I agree with most of what you said here. One thing that I would like to point out though. When designing the CTLS they put a CTSW in a full scale wind tunnel. One of the findings was that anything beyond 35° flaps had a increase in drag, but lift started to decrease. This is why they went to a maximum flaps of 35° on the CTLS, and now have reduced it to 30° on the newest airplanes. At least that is what I remember from the meetings at Sebring in 2008.

[FlyingMonkey]

Andy, I agree with most of what you said here. One thing that I would like to point out though. When designing the CTLS they put a CTSW in a full scale wind tunnel. One of the findings was that anything beyond 35° flaps had a increase in drag, but lift started to decrease. This is why they went to a maximum flaps of 35° on the CTLS, and now have reduced it to 30° on the newest airplanes. At least that is what I remember from the meetings at Sebring in 2008.

 

Fair enough, I kept my discussion to the 30° setting because there seems to be more controversy over the 40° setting.  That setting is nice to steepen up an approach, but I agree it's not helping the lift/drag ratio profile.  Does it actually *decrease* lift, or just increase drag a lot more than it increases lift?

 

What are the new settings on the newer CTLS?  -6/0/15/30 only?  It seems they could have left 35 in there and just cautioned against using it for normal landings.  It is always nice to have options.  

[sandpiper]

I will add once again that I teach students how to land with all flap settings, I just start with 15° because it is easier to learn how to land the airplane.

Tom - agree completely. I don't instruct much anymore but I would apply this to both primary students and anyone transitioning to the CT. Once 15 is mastered, then I would teach, and require proficiency in, all configurations before signing off.

[gbigs]

That is *your* standard landing configuration.  I don't think you'll find that as a standard recommendation anywhere in the POH.

 

Of course 30° & 40° flap settings increase drag substantially...that's kind of the point.  They also generate substantial lift to offset the drag.  As long as you have either:

 

A ) A short enough distance to the runway, or; 

 

B ) A functioning engine

 

The excess drag is immaterial.  You are going to come in steeper and slower, and you are going to have less landing energy to dissipate on the runway.  This is *highly* desirable for a safety standpoint.  To compare, for approach you use 62kt @ 15° and in light winds I use 52kt @ 30°.  In energy terms at gross weight of 1320lb:

 

1320lb at 62kt = ~224,000 foot pounds of potential energy.

 

1320lb at 52kt = ~157,000 foot pounds of potential energy.

 

That's almost exactly a 30% difference.  We both have to get the airplane stopped (or nearly so) on the runway, so we each have to basically get that energy down to approximately zero, in the same distance.  You have a harder problem, because you have to get an extra 30% energy out of the airplane.  But you refuse to slow down, so that leaves exactly two ways to dissipate energy:

 

1) Distance

 

2) Friction

 

You can either land longer, allowing the airplane to float until the speed bleeds off (see, you still have to slow down!) to a point where the airplane will allow you to land it, or you can generate a lot of frictional heating.  In other words, plant the airplane as soon as possible and get on the brakes as hard as you safely can.  I still don't think you are going to be able to get that additional 30% of the total energy out in a similar distance, no matter how white-hot you make the brake discs...

 

But wait, there's more!  You said "15 @ 62 over the numbers"...so you are not slowing at all, all the way down.  If the wind is calm, I often let the speed come down as I get close to the runway (over the numbers, maybe 20-30ft high) , as low as 48kt.  In other terms, ~134,000 lb/ft of energy, or 40% (!) less than your plane has at the same point.  At that speed I only have to dissipate about 4-6kt to get the airplane to the stall (landing) speed of ~42kt.  At the same height, you have to burn off 20kt to get to the same speed.  You are not in contact with the ground to melt the brakes, so you have one option:  float.

 

Question:  How would you land on a short runway, say 1700-2000ft long? 

 

No. It is the standard landing config for other than short runways and accounting for moderate wind and/or gusts.  See POH 4.2.14.

 

The POH warns: "The maximum flap position (30 degrees) should be used to land on very short runways under favorable wind conditions (no crosswind component, very light wind and low gusts).

 

62kts over the numbers after leveling produces the correct amount of energy in order to sink and flare at idle under standard conditions.   The amount of runway will vary with density altitude.  At 3000 feet DA which is how I fly most of the time the POH states 900 feet of runway is needed.  I often need less than that...

 

The higher lift and drag associated with fully extended flaps allows a steeper and slower approach to the landing site, but increases handling difficulties in aircraft with very low wing loading (the ratio between the wing area and the weight of the aircraft).  The FDCT has a very low wing loading profile which could explain why the CT will tend to drop onto the runway when max flaps are used.

 

I also pointed out to you that YOUR POH for the SW has all your numbers in CAS.  You need to find out what your IAS numbers are if you want to follow the design criteria for your aircraft.

[coppercity]

Can a person do full flap landings in a CT? Sure they can. Trying to teach a student to land a CT with full flaps from the beginning would be like trying to teach someone how to fly a tailwheel airplane in a P51. In theory it can be done, but the chance of something bad happening is far greater.

 

Just so you know I always do some full flap landings and some zero flap landings with the student prior to solo. Just after solo I teach short and soft field take offs and landings and we use full flaps conditions permitting for these. My recommendation is still 15° flaps for normal landings. Like I said before if done properly the 15° landing only increases touchdown speed by a couple knots, and I would rather give up a 2 knot increase in speed to lessen the chances of damage due to a hard landing.

 

My guess is what I want to see from a student when landing is similar to what you want to see except for the flap setting in the CT.

 

I agree Tom, and follow a similar process with my students.  I now have over 2000hrs in CT's and following this guidance has been successful for me and my students the last 7 years.

[Tom Baker]

No. It is the standard landing config for other than short runways and accounting for moderate wind and/or gusts.  See POH 4.2.14.

 

The POH warns: "The maximum flap position (30 degrees) should be used to land on very short runways under favorable wind conditions (no crosswind component, very light wind and low gusts).

 

62kts over the numbers after leveling produces the correct amount of energy in order to sink and flare at idle under standard conditions.   The amount of runway will vary with density altitude.  At 3000 feet DA which is how I fly most of the time the POH states 900 feet of runway is needed.  I often need less than that...

 

The higher lift and drag associated with fully extended flaps allows a steeper and slower approach to the landing site, but increases handling difficulties in aircraft with very low wing loading (the ratio between the wing area and the weight of the aircraft).  The FDCT has a very low wing loading profile which could explain why the CT will tend to drop onto the runway when max flaps are used.

 

I also pointed out to you that YOUR POH for the SW has all your numbers in CAS.  You need to find out what your IAS numbers are if you want to follow the design criteria for your aircraft.

Just so you know the version of the POH to which you refer is not available online for all to see, and it is different than what is published for the CTSW. There are more CTSW owners on this site than those who own a CTLSi.