the dreaded base to final turn

[DonMuncy]

My Alpha System is calibrated w/ flaps and gear up. The flaps just give an added layer of protection.

No, I don't think anything can physically measure angle of attack. Mine measures differential pressure at two points and converts that to "where the stall takes place", which is essentially critical AOA. 

[aviatoreb]

Are these calibrated to anything other than full flaps and gear down? Do they actually measure AOA?

 

They are usually called AOA indicators even if they are not measuring AOA in calibrated degrees.  I also have alpha systems.  You calibrate it yourself to the stall point in a recomemnded configuration which is clean.  Then to another point which is more like a low cruise, to teach the device how to spread the scale.  So then what you have is a lift reserve device.

[Bob - S50]

Yes you can stall a Mooney in a steep banked turn even if you do not hold the nose up. The 60 degree banked clean stall speed in my aircraft is about 90. In practicing steep spirals for commercial I could get the stall warning to go off at 85 kts. in a descending spiral just by steepening the bank to 60 degrees. There is not enough vertical lift component left.

I think we are saying the same thing but I'm not sure so....

 

The 60 degree bank angle stall speed is for level flight.  30 degrees of bank requires 1.15 G's to maintain level flight. 45 degrees of bank requires 1.41 G's, 60 degrees of bank requires 2 G's, 70 degrees requires 2.92 G's, 80 degrees = 5.76 G's, and finally 90 degrees is impossible (unless you use the rudder and fuselage to act as an elevator and wing).

 

Lift is a function of the square of velocity.  So 2 G's will result in a stall speed which is the square root of 2 (which is 1.41) times the wings level stall speed.  If your stall speed wings level is 57 knots, your 60 degree bank stall speed for level flight should be about 80 knots.  That just happens to be the speed I fly base at.  So.... if I'm overshooting but on the proper vertical flight path, and I increase the bank to 60 degrees to stop the overshoot and pull back on the yoke to maintain my fight path, I'll stall.

 

Bank angle in itself will not cause a stall.  However, if you increase the bank one of two things will have to happen:

 

1.  You'll have to increase the back pressure (AOA/wing loading/G's) to maintain level flight or current rate of descent/flight path.  This can cause a stall.

 

2.  Your nose will fall causing an increase in sink rate and airspeed.  This is not a good thing when close to the ground.  You'll soon need pull back to arrest the sink rate and once again you could stall the plane.  However, if you roll out of the turn before you pull, you'll give yourself the best chance of stopping the sink rate before mother earth does.

 

Bob

[Bob_Belville]

 

2.  Your nose will fall causing an increase in sink rate and airspeed.  This is not a good thing when close to the ground.  You'll soon need pull back to arrest the sink rate and once again you could stall the plane.  However, if you roll out of the turn before you pull, you'll give yourself the best chance of stopping the sink rate before mother earth does.

 

Bob

Your plane still has a throttle?

[Wakeup]

Loved watching the Sun N Fun video. I was lucky last year and it wasn't too busy. Landed on my first skinny runway. Troy

[Ftlausa]

A stable approach after a properly flown pattern and flying by the numbers is obviously the cure for the stall/spin.  But, having practiced cross-controlled stalls for the fun of it, and having slipped the hell out of tail draggers on final (and occasionally my mid-body Mooney), I can say that the key is keeping the wings unloaded if you are going to slip/cross control, or keeping the ball centered and airspeed up if you are banking hard in the pattern. I don't see much reason to exceed 45 degrees in the pattern, but if you fly the pattern by the numbers, you should be sufficiently above stall speed prior to short final even if you accidentally put in a 60 bank or cross-control a little.  The first thing I do before slipping or banking hard in the pattern is look at the airspeed.         

[PTK]

Keep coordinated, 30 deg max bank and nose down. Simple really!

If nose is going up here then something is not right!

Bad things happen when the airplane is allowed to stray uncoordinated, AS is allowed to decay and the pilot forces it bent on salvaging the landing.

No where in the FAR's does it say that every approach must terminate to a landing!

[Bob - S50]

Your plane still has a throttle?

Yes it does.

 

However, if I increase bank and do not increase back pressure, throttle will not bring the nose up, it will just increase airspeed.  The only way throttle will bring the nose up is if the airplane is trimmed for a given speed.  Even then, only the component of lift that is pointed away from the ground will bring the nose up.  In level flight, that is all of it.  In 90 degrees of bank, that is none of it.  You get varying amounts at different bank angles.  At 45 degrees of bank, it is only about 70% of the lift vector.  That's why if you need to get away from the ground, you level the wings and then pull.  It points all your lift vector away from the ground.

 

Going to an extreme, roll your plane into 90 degrees of bank, the nose falls.  Add as much power as you like.  The nose is not going to come up.

 

Bob

[Bob_Belville]

Yes it does.

 

However, if I increase bank and do not increase back pressure, throttle will not bring the nose up, it will just increase airspeed.  

Bob

That's just silly. If you add power, everything else being equal, you will decrease rate of descent. We're talking practical attitudes in the landing pattern. If the plane is trimmed for 85 kts and you have to increase the bank from 30 to 45 degs to avoid overshooting final, you can add power to offset loss of lift if descent rate is going to be too great. There should be no instinct to yank back yoke and risk stall. For our vintage models 85 kts or so has a comfortable cushion until you're leveled up on final.  

[Hank]

Bob, I fly 90 mph in the pattern, and slow to 85 mph in the base-to-final turn.

[Mooneymite]

 

Going to an extreme, roll your plane into 90 degrees of bank, the nose falls.  Add as much power as you like.  The nose is not going to come up.

 

 

I try to avoid this type of base-to-final turn so that it is not my "final turn".   

[Bob - S50]

I try to avoid this type of base-to-final turn so that it is not my "final turn".   

 

Very wise grasshopper.

[Bob - S50]

That's just silly. If you add power, everything else being equal, you will decrease rate of descent. We're talking practical attitudes in the landing pattern. If the plane is trimmed for 85 kts and you have to increase the bank from 30 to 45 degs to avoid overshooting final, you can add power to offset loss of lift if descent rate is going to be too great. There should be no instinct to yank back yoke and risk stall. For our vintage models 85 kts or so has a comfortable cushion until you're leveled up on final.  

 

Try it and let me know how it works.

 

Climb to say 5000', slow to 85 knots.  Trim the airplane for hands off level flight.  Roll into a 30 or 45 degree bank turn.  Take your hands off the yoke.  Add power.  Let me know how well the nose comes up.

 

Without back pressure the nose will drop.  As the nose drops, airspeed will increase.  As it does, the airplane will try to pitch up to regain the trimmed airspeed.  However, at the trimmed airspeed, only a portion of the lift vector is pointed up.  Another portion is causing the turn.  At 45 degrees of bank, only 0.707 of the lift vector is pointed up.  Another 0.707 is pointed into the turn causing the turn.  In order for the vertical lift vector to equal your weight, you'll have to increase airspeed by about 20%.  So... if you start at 85 knots, I'm guessing the nose will not come back up to level until your airspeed increases to about 100 to 105 knots.

 

If you roll into a turn, or increase the bank, you ...must... increase back pressure or the nose will fall and you'll begin/increase your descent.  Adding power will allow you to maintain your airspeed while you are doing that.  If you do not add power to maintain airspeed, the aircraft will slow down and may get down to stall speed.

 

AKA, the final turn stall.

 

Bob

[GeorgePerry]

http://www.aopa.org/AOPA-Live.aspx?watch={153E8150-DE50-4658-9377-9C05DB2E60D6}

 

http://www.aopa.org/AOPA-Live.aspx?watch=%7B153E8150-DE50-4658-9377-9C05DB2E60D6%7D#ooid=NoMndlbDpMPxEDCuGI2hYTcaQwVSQUBO

 

2 different links to the same training video.   Should work now

[Bob_Belville]

http://www.aopa.org/AOPA-Live.aspx?watch={153E8150-DE50-4658-9377-9C05DB2E60D6}

Hi George, link returns an error for me...

[rq3]

AOA indicators

I need to install one

Check out the CYA-100 from Aircraft Spruce. True AoA, inexpensive, easy to install, FAA approved.

[rq3]

My Alpha System is calibrated w/ flaps and gear up. The flaps just give an added layer of protection.

No, I don't think anything can physically measure angle of attack. Mine measures differential pressure at two points and converts that to "where the stall takes place", which is essentially critical AOA. 

 

Don, your flaps do no such thing. A wing with flaps down will stall at a LOWER angle of attack than with flaps up. It will also stall at a lower AIRSPEED, which is what confuses most folks. The wing stalls at ONE angle of attack, and at an infinite number of airspeeds.

A vane, like the CYA-100 (which I make and market) measures TRUE angle of attack. Differential pressure does not, although it may be good enough for government work.

 

Rip

[DonMuncy]

You apparently know more about it than I do.

[rq3]

They are usually called AOA indicators even if they are not measuring AOA in calibrated degrees.  I also have alpha systems.  You calibrate it yourself to the stall point in a recomemnded configuration which is clean.  Then to another point which is more like a low cruise, to teach the device how to spread the scale.  So then what you have is a lift reserve device.

 

Pressure differential devices act just as you say. Vane devices, like my CYA-100, measure TRUE angle of attack. The CYA-100 calibration for stall is done "dirty" (full flaps, gear down, landing configuration) because that is the worst case angle of attack. NOT the worst case airspeed. The two have nothing to do with one another.. You can stall at ANY airspeed. You WILL stall at only ONE angle of attack, regardless of weight, airspeed, or bank angle.

 

Rip

[rq3]

I seriously think these things could save a lot of people if we all had them installed and were trained to use them.

 

I want one!!!

Then you need the CYA-100, available from Aircraft Spruce. The only inexpensive FAA approved TRUE angle of attack system for general aviation.

But if you don't like it, buy one of the others. Please. I truly believe these things can save lives!

 

Rip

[rq3]

Are these calibrated to anything other than full flaps and gear down? Do they actually measure AOA?

The CYA-100 meaures true angle of attack, defined as the angle between the relative wind and the airfoil chord.

It can be calibrated (with two button presses) anywhere you like. I specify "stall" AoA at full flaps with gear down,

since that is a "worst case" condition.

 

Rip

[rq3]

You apparently know more about it than I do.

Don, don't be embarrassed. Most pilots don't realize that a wing stalls at a LOWER angle of attack with flaps than without.

Even the other Angle of Attack manufacturers have this wrong. And that's why they have their calibration wrong,too.

 

Rip

[DonMuncy]

How many degrees is the typical angle of attack on most Mooneys. Does the CYA-100 read down to a half degree.

[rq3]

How many degrees is the typical angle of attack on most Mooneys. Does the CYA-100 read down to a half degree.

Don, define the condition please. Most GA wings stall somewhere between 16 to 18 degrees. The CYA-100 resolution is about 0.35 degrees

[DonMuncy]

You will have to pardon my ignorance. I have not seen the display on a CYA-100. I just wondered what number of degrees most pilots were seeing on your display at the place where they calibrated the stall on the instrument.