Slow Flight

[Dan Kent]

I own a Sting S4 and went out this weekend and did some slow flying. I did clearing turns and then pulled the throttle back with no flaps and could easily fly at 40 kts. I was probably about 150 lbs under gross.

 

The S4 has 4 flap settings and they are not measured in degrees (except 0 flaps), but the 4th setting is very pronouced and take back presssure on the stick to offset it as there is not enough trim to counteract it. The S4 also has split flaps.

 

I flew for several minutes with full flaps at 28 knots but upped the engine speed to 30 knots for several more minutes.

 

Anyway I thought I was doing close to full stall landings, but now don't think I am, as I cross the numbers at 50 kts and doubt I'm skilled enough to hold off more than a 20 kt speed bleed.

 

Just curious as to what the CT's can do in slow flight.

[Ian]

Isn't there an issue with very slow flight of position error on the ASI - inevitably you will be in a very nose up attitude so the airflow into the pitot tube may not be as normal so i believe there is a point at which you can no longer trust the air speed indicator?

 

Certainly checking the stalling speeds on the CTLS I find the POH is pretty much spot on - 39kts with 30 flap down and there's a gentle mush downwards rather than a violent stall - put in some power and you can happily "fly" along at or just above that speed.

[sandpiper]

Dan - I kind of doubt you were actually doing 28K. Airspeed indicators are notoriously wrong, especially at slow speeds. I remember some of the Cessnas I used to fly could be slowed to zero indicated. Of course, we were doing more than that.

[CT4ME]

Whenever I slow less than about 70kts, I begin to watch the GPS ground speed. When there is little wind, I figure it's more accurate. Thoughts?

tim

[Ian]

Whenever I slow less than about 70kts, I begin to watch the GPS ground speed. When there is little wind, I figure it's more accurate. Thoughts?

tim

 

I think I trust my ASI reading right down to stalling speeds - I wouldn't use the GPS ground speed for anything critical - even though you say "little wind" you can't ever know 100% what the wind is at any particular moment so apart from calculating time to waypoint I'm not sure what else I'd use it for when flying VFR?

[Ed Cesnalis]

Sounds dangerous. We see winds from a single point, like your EFIS or a wind sock or an automated weather system. In all cases we get only direction, velocity and perhaps gust or variability information. It can be a very misleading picture.

[CT4ME]

I don't "only" rely on the gps speed, but use it to compare/contrast with pitot speed. As mentioned by others here over the years, the airspeed indicators can vary considerably in their accuracy. When we fly in groups, there have been easy 10kt variations. When I see a bunch of CTs setting together it's amazing the variation you see in the angle of the pitots.

BTW... my airspeed guage is due for rebuild... it's sticky.

tim

[Dan Kent]

Thanks all.

 

BTW when I was doing flight training with my CFI, we were practicing slow flight in a very strong headwind, and our ground speed was negative on the Dynon, and you could tell we were going backwards across the ground.

 

He said he had never done this before and took a picture of the Dynon screen.

[Ian]

This side of the Atlantic it's called a vertical circuit - did it in a C150 many years ago!

[Ed Cesnalis]

It's the helicopter effect. The wind matches your thrust and lift so you hover, or even go backward.

 

How about wind's headwind component matches or exceeds your airspeed, so you have zero or negative ground speed?

 

What units of measure do you use to measure thrust?

How do you add thrust to lift?

[Dan Kent]

Just to close the loop on this, I contacted Dynon and they suggested that I do a zero pressure airspeed calibration. I've done that and it had quite an effect on my airspeed particularly low airspeed.

 

Yesterday I went out and did some stalls and with full flaps it was breaking around 32-34 kts. No flaps was around 36-38 kts.

[Doug G.]

I practice slow flight fairly often, both straight and level, and turning (takes quite a bit of added power to maintain altitude and speed with the loss of lift in the turn). Teaches you to be active on the rudder!

It is difficult to get my CTLS to stall with full flaps (35 deg. on the CTLS. When the stick gets all the way back with no power it will eventually mush and that is about it. It happens somewhere less than 39kias, which is where it is supposed to be. (I don't know if the redundant pitot system makes that any more accurate or not.)

 

[Roger Lee]

Hi Doug,

 

That sounds pretty normal from what I have seen over the years. Mine is about the same.

[Dan Kent]

I practice slow flight fairly often, both straight and level, and turning (takes quite a bit of added power to maintain altitude and speed with the loss of lift in the turn). Teaches you to be active on the rudder!

It is difficult to get my CTLS to stall with full flaps (35 deg. on the CTLS. When the stick gets all the way back with no power it will eventually mush and that is about it. It happens somewhere less than 39kias, which is where it is supposed to be. (I don't know if the redundant pitot system makes that any more accurate or not.)

I had somewhat of the same issue yesterday except I still had up elevator available, but the plane didn't want to break, just kept buffeting. If I had pulled back some more it would have broken but I was trying to maintain alt. Other stalls eventually broke, but recovered in less than 200 feet of alt.

 

I also agree on slow flight. I like to go slow flying every so often. It seems to help me shake off the rust if I haven't flown in a couple of weeks.

[FlyingMonkey]

If I ever saw a level flying speed significantly below published stall speeds, I'd suspect low-speed pitot error.

[S4Flier]

If I ever saw a level flying speed significantly below published stall speeds, I'd suspect low-speed pitot error.

Not so fast. Published stall speeds are at MTOW and stall speed is proportional to square root of 'actual weight'/MTOW. It is not uncommon for me to fly solo at 200+lbs below MTOW. sqrt(1120/1320) = 92%. Clean stall on the Sting is in the manual at 44 kts (IAS) * 0.92 = 40.5kts, dirty is 39kts * .92 = 36kts. Didn't sound like the folks above were flying slowing than what may have been their real stall speed.