Slow Flight and the Red Arc

[Brian E.]

Fellow Mooniacs - with the Winter upon us I'm on the slow train for completing my CFI training in our beloved C.  One of the challenges I am facing is slow flight and the prop no continuous operating range (65C, B hub, 2 blade hartzell, 2000 - 2250 rpm red arc).  If I recall correctly, configuring the plane for  75 MIAS (1.3 * VSO), gear extended, full flaps and prop full forward requires ~16.5 or 17 in. MP giving me just about  2150 - 2200 RPM on the prop--solidly in the red arc.

  When I did my commercial training in the Mooney I never hung out in that zone, I just transited it on the way to power off stalls.  Now I'm having to instruct mock students on slow flight and find that it requires sustained flight in the red arc to demonstrate proficiency while in this configuration.  Anything I'm missing?  Do you just not perform slow flight training in your aircraft? 

  Appreciate your insight.

[Hank]

What is it for gear up and Takeoff flaps?

I've done plenty of slow flight with CFI / CFIIs in my C, but also not that fast, we had the stall horn blaring all the time. She's very controllable. But I don't remember the power settings or configuration exactly, it's been a while. And the Feds don't like this method any more . . . .

[carusoam]

Slow flight training is important for every aircraft...

We get a feeling for the onset of stall buffeting this way....
 

Brian what keeps you from using a low power setting on either side of the ‘red’ arc..?

How long are you flying around in slow flight one minute, two, ten? A couple of 360s?

 

Lets see if @midlifeflyer Mark is around...

Best regards,

-a-

[Brian E.]

7 hours ago, carusoam said:

Brian what keeps you from using a low power setting on either side of the ‘red’ arc..?

How long are you flying around in slow flight one minute, two, ten? A couple of 360s?

-a-

My tongue in cheek response to the 1st question--Bernoulli, Newtown and the PP ACS

As you recall in that configuration you're in the area of reverse control.  The power setting controls your altitude--mo' power more altitude, less power less altitude. And, since the prop is full forward the MP directly controls the RPM.

How long are we talking about?  It really should be a 5 - 10 minute evolution.  The ACS expects the applicant to demonstrate "coordinated straight-and-level flight, turns, climbs, and descents with the airplane configured as specified by the evaluator without a stall warning."  As you can imagine a seasoned pilot could do that pretty quickly but mock students would take a bit more time as would a real student.

 

[M20F]

Rangers move, slow flight is for Comanches.  

[midlifeflyer]

9 hours ago, carusoam said:

Lets see if @midlifeflyer Mark is around...

He is, but can't help. I know I've done it but it's been a while. And before the redefined slow flight (stall horn not blaring). Unfortunately, my friend's C is down for maintenance. I'm curious now.

[RobertGary1]

19 hours ago, Hank said:

What is it for gear up and Takeoff flaps?

I've done plenty of slow flight with CFI / CFIIs in my C, but also not that fast, we had the stall horn blaring all the time. She's very controllable. But I don't remember the power settings or configuration exactly, it's been a while. And the Feds don't like this method any more . . . .

That's old.  Now if the stall horn goes off while doing slow flight its a checkride failure. New standards.

 

A. Maneuvering During Slow Flight

CA.VII.A.S4
Accomplish coordinated straight-and-level flight, turns, climbs, and descents with the
aircraft configured as specified by the evaluator without a stall warning (e.g., airplane
buffet, stall horn, etc.)

 

-Robert, CFII

Edited February 3, 2021 by RobertGary1

[Ragsf15e]

I don’t have a good answer for you, but has a dpe really failed someone for their stall horn going off during slow flight?  What is our world coming to?  Might as well fly it at 99 kts!  So unless I missed something, the ACS doesn’t cause us to teach students to fly close to the stall unless they actually intend to stall... so no more “getting the feeling of mushy controls, coordination, buffet, etc?”  We will be worse pilots without that training.

I might have a discussion with the dpe about aircraft limitations in regards to rpm.  If you try it clean or configured with gear and no flaps vs gear and full flaps, you can probably find something that works to keep you from prolonged ops in the red.  If the dpe agrees with that configuration, you should be ok.  My airplane has “no continuous ops” zone which to me is a long time.  You should be able to at least transit your zone a few times.

[Hank]

1 hour ago, RobertGary1 said:

That's old.  Now if the stall horn goes off while doing slow flight its a checkride failure. New standards.

 

A. Maneuvering During Slow Flight

CA.VII.A.S4
Accomplish coordinated straight-and-level flight, turns, climbs, and descents with the
aircraft configured as specified by the evaluator without a stall warning (e.g., airplane
buffet, stall horn, etc.)

 

-Robert, CFII

That's exactly what "the Feds don't like this method any more . . . " means.

Reading comprehension, people. Of the entire post, not just the beginning. 

[RobertGary1]

2 hours ago, Ragsf15e said:

I don’t have a good answer for you, but has a dpe really failed someone for their stall horn going off during slow flight?  What is our world coming to?  Might as well fly it at 99 kts!  So unless I missed something, the ACS doesn’t cause us to teach students to fly close to the stall unless they actually intend to stall... so no more “getting the feeling of mushy controls, coordination, buffet, etc?”  We will be worse pilots without that training.

 

I don't disagree. Many said the same when spins were removed from the curriculum. Although oddly the FAA never said slow flight was for the purpose of learning the pre-stall sensations (although that is how I taught it anyway) they said it was in be proficient if you needed to fly slow for situations like a congested traffic pattern. Can't imagine a student pilot flying slow in the pattern for spacing (well, for gliders is the norm).

 

-robert

[markgrue]

3 hours ago, RobertGary1 said:

That's old.  Now if the stall horn goes off while doing slow flight its a checkride failure. New standards.

 

A. Maneuvering During Slow Flight

CA.VII.A.S4
Accomplish coordinated straight-and-level flight, turns, climbs, and descents with the
aircraft configured as specified by the evaluator without a stall warning (e.g., airplane
buffet, stall horn, etc.)

 

-Robert, CFII

That is a sad state of affairs....  We used to take pride in keeping the stall horn on without getting a full stall.  It was an indication of the ability to precisely control the aircraft in an unstable situation. 

 

Mark 

[Vance Harral]

Over the course of 17 years, five complex endorsements, three instrument ratings, one commercial certificate, one CFI, and one CFII, I'm sure our airplane has accumulated "several" collective hours in the red RPM arc.  Neither the prop nor the engine has fallen off the airplane yet, though admittedly that's just one data point.

[lamont337]

5 hours ago, RobertGary1 said:

CA.VII.A.S4
Accomplish coordinated straight-and-level flight, turns, climbs, and descents with the
aircraft configured as specified by the evaluator without a stall warning (e.g., airplane
buffet, stall horn, etc.)

Just above that it S3 for the speed:

Establish and maintain an airspeed at which any further increase in angle of attack, 
increase in load factor, or reduction in power, would result in a stall warning (e.g., airplane
buffet, stall horn, etc.).

75 would be too fast in my C, no mention of Vso 1.3

Edited February 4, 2021 by lamont337

[RobertGary1]

23 minutes ago, lamont337 said:

Just above that it S3 for the speed:

Establish and maintain an airspeed at which any further increase in angle of attack, 
increase in load factor, or reduction in power, would result in a stall warning (e.g., airplane
buffet, stall horn, etc.).

75 would be too fast in my C, no mention of Vso 1.3

Yea it repeats the same. No stall horn. 

Edited February 4, 2021 by RobertGary1

[PT20J]

I believe that the idea is to train so that a stall warning elicits immediate action to add power and reduce angle of attack. Flying around with the horn blowing defeats the training objective. Will this make safer pilots? Who knows? Pilots seem to regularly land with the gear warning blaring, so I guess they can spin in while ignoring the stall warning just as well.

Skip

[RobertGary1]

1 hour ago, PT20J said:

I believe that the idea is to train so that a stall warning elicits immediate action to add power and reduce angle of attack. Flying around with the horn blowing defeats the training objective. Will this make safer pilots? Who knows? Pilots seem to regularly land with the gear warning blaring, so I guess they can spin in while ignoring the stall warning just as well.

Skip

It’s one reason I added the voice annunciator it’s hard to ignore “check landing gear”. 
I’d like to see Garmin come up with a solution. It already knows if I’ll not landing and gives me terrain warnings. Just invert that logic. 

[Brian E.]

6 hours ago, lamont337 said:

Just above that it S3 for the speed:

Establish and maintain an airspeed at which any further increase in angle of attack, 
increase in load factor, or reduction in power, would result in a stall warning (e.g., airplane
buffet, stall horn, etc.).

75 would be too fast in my C, no mention of Vso 1.3

 I'm surprised that 75 is too fast.  I stall right at 58 MIAS which brings me to the 75.  And in practice if I want a bit of a buffer from the stall horn due to turbulent conditions 78 is preferred.

  

[midlifeflyer]

13 hours ago, markgrue said:

That is a sad state of affairs....  We used to take pride in keeping the stall horn on without getting a full stall.  It was an indication of the ability to precisely control the aircraft in an unstable situation. 

 

I thought the protests over this were much ado about nothing. Even got in trouble with Machado for saying I thought his arguments with John King were just a pi$$ing contest.  I think the FAA's purpose in removing the stall warning blaring from slow flight was a good one. And all you have to do is watch a few videos of pilots unintentionally  landing gear up while completely ignoring the gear warning blaring away to understand it.

You don't get failed if the warning sounds during slow flight. You get failed if you don't correct the condition while remaining in the slow flight condition, which also requires demonstration of precise control. If we train to correct warnings, we will correct warnings. If we train to ignore warnings, we will ignore warnings.

 

(I didn't see @PT20J's post when I wrote this.)

[lamont337]

5 hours ago, Brian E. said:

 I'm surprised that 75 is too fast.  I stall right at 58 MIAS which brings me to the 75.  And in practice if I want a bit of a buffer from the stall horn due to turbulent conditions 78 is preferred.

  

I take that back, I was going off of 63 which is the bottom of the white arc for mine and not including the horn going off prior. To really dial it in I’d probably go horn plus 5, which would give you a 5 knot buffer on either side. Sorry for my confusion as that doesn’t solve the RPM issue. 

[gsxrpilot]

2 hours ago, midlifeflyer said:

You don't get failed if the warning sounds during slow flight. You get failed if you don't correct the condition while remaining in the slow flight condition, which also requires demonstration of precise control. If we train to correct warnings, we will correct warnings. If we train to ignore warnings, we will ignore warnings.

My, very old school, primary CFI drilled this into me. Don't ever sit and listen to a warning sound, buzzer, alarm, alert, whatever. Turn it off immediately. This is especially critical with the gear warning horn. Don't listen to it. Turn it off. That means either extend the gear or add power. But one way or the other, turn off the horn.

[cctsurf]

32 minutes ago, gsxrpilot said:

My, very old school, primary CFI drilled this into me. Don't ever sit and listen to a warning sound, buzzer, alarm, alert, whatever. Turn it off immediately. This is especially critical with the gear warning horn. Don't listen to it. Turn it off. That means either extend the gear or add power. But one way or the other, turn off the horn.

I'm of the old school that flew the entire slow flight portion of my check ride with the horn blaring.  It impressed my dpe (who was really old school...and old...and has since passed on.).  However, I could get 100% behind this, especially if the stall warnings actually indicated something approximating a stall.  Perhaps mine needs to be adjusted, but it goes off way above stall.

[Hank]

18 minutes ago, cctsurf said:

I'm of the old school that flew the entire slow flight portion of my check ride with the horn blaring.  It impressed my dpe (who was really old school...and old...and has since passed on.).  However, I could get 100% behind this, especially if the stall warnings actually indicated something approximating a stall.  Perhaps mine needs to be adjusted, but it goes off way above stall.

It's supposed to be ~5 knots or so above stall. There's no benefit to having the alarm go off to tell you "Hey, look out, you're in a stall!" It gives you advance warning so you can correct it, if the stall is not what you want to happen.

[midlifeflyer]

6 hours ago, gsxrpilot said:

My, very old school, primary CFI drilled this into me. Don't ever sit and listen to a warning sound, buzzer, alarm, alert, whatever. Turn it off immediately. This is especially critical with the gear warning horn. Don't listen to it. Turn it off. That means either extend the gear or add power. But one way or the other, turn off the horn.

When I do complex transitions I teach that in normal operations you should never hear the gear warning. If you do, you did something wrong. Even more, "no matter how you explain it, your wife/husband/partner/boyfriend/girlfriend will hate that sound."

[Hair Helmet]

I suppose the simple solution is a composite prop without an rpm restriction.  Apparently the harmonics can crack the crank if we hang out there too long....

[Raymond J1]

The red arc mainly concerns the two-blade "Hartzell" propellers, sensitive to a "brineling" of the blade feet below 2350 rpm. This is a well-known fatigue problem. Tri-blades whose harmonic rank H3 is out of resonance with the motor H3 are not affected. The "MC Cauley" two-blades have a slightly lower H3 level than the "Hartzell".

Edited February 11, 2021 by Raymond J
adjust terms and orthograph