IFR Flight Profile

[jaylw314]

22 minutes ago, bob865 said:

Reviving my old post here.  I'm plugging my way through the training, finally!  It's been fun, though a challenge with the short days since I'm trying to fly after work which means I'm training primarily in the dark.  All of the above info has helped me greatly jump straight in.  Thank you all again.  I have new questions though. 

 What I'm finding is my biggest struggle is holding altitude to the PTS (+-100ft).  The Mooney seems to be a good bit more unstable in pitch than like a cessna or piper than I've flown previously.  Maybe it's not really as bad as it seems right now since I'm kinda anal and a bit of a perfectionist, but does anyone have any pointers on helping to improve how well I hold altitude?

If you are noticing what I noticed, I think it is because the Mooney is a low-drag airframe, so it takes TIME to get a stable airspeed and altitude.  Once you change either, it takes a relatively long time for those to stabilize because the power is so low for any given speed in level flight.  If you trained in anything like a C172 or Cherokee, you learned to apply some yoke pressure, then trim to relieve that pressure.  In the time it takes you to reach for the trim knob (or crank) and start trimming, those high-drag airframes have already stabilized.  I might suggest whenever you change attitude, count to 3 before you trim it out (or get used to trimming once, then trimming again a few seconds later).

Do you think your scanning also needs to pick up speed?  That might also be an explanation for problems holding altitude precisely?

[Bob - S50]

I second that.  Trim, trim, trim.  If it is trimmed properly you should be able to take your hands off the yoke for at least 15 seconds with no noticeable change in attitude or altitude.

Use a light touch.  Any time you look away from the ADI for any appreciable amount of time, try holding the yoke between two finger tips.

Also, remember, higher speed requires finer adjustments.  If you fly a cessna at 90 KTAS a 1 degree pitch change will create about a 150 fpm (+/-) climb or descent.  If you are in your Mooney going 150 KTAS, that same 1 degree pitch change will create about a 250 fpm VS.

[ilovecornfields]

My experience transitioning to a Mooney (from an Arrow) is that it required a lot more trim changes to get stabilized. I think this is because of the much greater speed and power. As Jay pointed out, it takes a while to reach equilibrium. I think the nice thing about the Mooney is that these changes are pretty predictable. As you level off from climb, for example, you will need left rudder trim and forward elevator and more of this as you speed up. Once it gets to its cruise speed, I don’t think it’s any less stable than a 172 or Arrrow, just takes a while to get there.

Passed a 172 yesterday with a 70 kt overtake. My son said “that Cessna’s flying backwards!”

[Skates97]

23 minutes ago, Immelman said:

A property rigged mooney is a very stable IFR platform. If you are having trouble with altitude hold I would look very carefully at your trimming technique and then any issues with the airplane rigging. The problem is most likely the pilot, and the good news is that only takes some practice to fix.

Get to altitude, get the airspeed where you want it, set the power to hold that airspeed, and trim-trim-trim as you get that dialed in. Once property trimmed, if you don't touch anything, I think you'll see that your airplane will fly as if it were on rails. The final trim adjustments are very subtle. I use my electric trim for big changes, but use the manual trim wheel to adjust just those final touches as you have finer control... very very small movements.

 

The one thing I had to get used to was how little you can move the trim wheel and have it make a difference. 

Also consider the air you are flying in. If it is summertime here out west and I am flying in the afternoon I am frequently making small adjustments to the trim due to the stability of the air. Other times I can get it trimmed out and like Immelman said, it is like it is on rails.

[carusoam]

Great discussion on trim technique...

Something about IFR training in December...

Are you getting high winds near the ground with that?

Lots of vertical wind currents?

I did my IR training in December 2009 or so, using a C172 (between Mooneys)..., in N. Jersey...

Trying to hold altitude in a downdraft on the backside of a mountain became more than the C172 was capable of... brief descents in the dark, heading for trees... with your CFII....

What kind of weather are you encountering?

can you go higher for this type of work?  Or are stuck doing approach procedures near the ground?

Best regards,

-a-

[bob865]

4 minutes ago, carusoam said:

Great discussion on trim technique...

Something about IFR training in December...

Are you getting high winds near the ground with that?

Lots of vertical wind currents?

I did my IR training in December 2009 or so, using a C172 (between Mooneys)..., in N. Jersey...

Trying to hold altitude in a downdraft on the backside of a mountain became more than the C172 was capable of...

What kind of weather are you encountering?

can you go higher for this type of work?  Or are stuck doing approach procedures near the ground?

Best regards,

-a-

I think your point may be the most akin to my situation.  Since you mentoined it, I'm thinking about it and I don't know if I have flown under the hood yet without at least a little bump.  A may be too concerned at this point.  Add that to what @jaylw314 said above about it taking some time to stabilize and I think we have my situation.  I'm probably a bit too heavy handed on the trim wheel too.  So taking to heart @Immelman's comment and being lighter on the wheel.  Definitely some things to try next time I fly.

Back to the turbulent air topic, I don't see how anyone could be expected to keep to +-100ft in turbulence in real life, or am I wrong?  Are you guys able to do this?  Or what do you see in the real world?

[carusoam]

In the real world...on the east coast, above 5k’ agl... the air is stable as glass.... get above the lowest level of clouds.

holding 100’ is a challenge, but can be accomplished pretty easily...

It is going to be important when the test day arrives... select the best test day... or be ready to discuss the expectations of the crummy weather and the test giver’s expectations.... based on you well orchestrated experience...

Same thing happened for the PPL... seasonal changes happen...

Your knowledge is being tested more than the limits written in the book...

So... get these trim techniques worked out at altitude.... you can do this on your own, VFR...

get a feeling for flying level... then add tiny disturbances to the trim to see how big the tiny disturbance is....

When flying the pattern, what trim procedure are you using? Hint... you have to do this pretty quickly or the next configuration change happens on the next leg already... or next county if you are waiting too long. (reasons new Mooney pilots fall behind the airplane...)

Having a Mooney CFII is great for learning fine detail for these techniques... the MAPA book is pretty helpful for this too...

In real life... push the alt button on the KAP150, the light comes on... the altitude settles in right where you pushed the button....the plane will accelerate while holding altitude... pretty easy.

But that’s not what the training is about... 

Expect a lot of testing of your multi-tasking skills...  as soon as you are level and trimming... you will get assigned a climb.   You are climbing steadily... you get assigned a new altitude... you are level doing slow flight... you get a new speed assigned... always use the yoke, then trim off the pressure....

finer adjustments... hold the yoke, trim off the pressure... then release the yoke... does the nose climb or descend...? Hold the yoke, trim, release the yoke...climb/descend? Again and again.... smaller and smaller adjustments...

PP, not a CFI...

Best regards,

-a-

[bob865]

8 minutes ago, carusoam said:

In real life... push the alt button on the KAP150, the light comes on... the altitude settles in right where you pushed the button....the plane will accelerate while holding altitude... pretty easy.

I've searched my PC over and over and just can't seem to find the ALT HOLD button.  I guess I'll just have to stick to my dual installed Mark 1 Eyeballs for monitoring and 5 digit control manipulators for the actuation.  

[Hank]

6 hours ago, bob865 said:

 . . . guess I'll just have to stick to my dual installed Mark 1 Eyeballs for monitoring and 5 digit control manipulators for the actuation.  

I've been upgraded to Mk II, also called "four eyes." Must be why I'm so good at monitoring altitude.  

[Immelman]

I will also add if you are working on your IR to tighten up your tolerances significantly. If you train your technique to hold altitude within 20' (the small tick on an ordinary altimeter), then 100' for your check-ride will be nothing, and you will find IFR flight significantly easier because your good technique has the airplane staying where it should, not wandering away while your attention is diverted to other tasks... that time sharing is what makes single pilot IFR, especially without an autopilot, very challenging. Stack the deck in your favor.

I will also... and I say this softly as I am a CFI and I know it isn't 100% correct per the 'book', but I also find that doing those last adjustments with trim alone, or with very little yoke, works. The yoke is a big lever. The trim wheel is a fine instrument. 

Once you have the airplane trimmed out it is a thing of beauty.

As far as your comment on turbulence: turbulence and chop tend to even themselves out. What I am saying above with a tight tolerance applies to developing your technique in smooth air. Do this practice on a nice, smooth day, no IFR training. Then, use the same technique when its bumpy... you will see some altitude deviations they will likely correct themselves. If its something more significant like wave, or convective cloud (there is very little reason to fly in Cu clouds, its just no fun). well, then you have to take a corrective action.

 

 

Edited December 22, 2018 by Immelman

[PT20J]

10 hours ago, bob865 said:

What I'm finding is my biggest struggle is holding altitude to the PTS (+-100ft).  The Mooney seems to be a good bit more unstable in pitch than like a cessna or piper than I've flown previously.  Maybe it's not really as bad as it seems right now since I'm kinda anal and a bit of a perfectionist, but does anyone have any pointers on helping to improve how well I hold altitude?

There's nothing particularly special about trimming a Mooney. It's a matter of nailing the attitude and taking the care to get it properly in trim. With a lower performance airplane like a C-172 or a PA28, the airplane doesn't gain or lose altitude very quickly with small pitch changes, so if they are slightly out of trim you don't notice the excursions as much. With a higher performance airplane, it will quickly gain or lose altitude with very small pitch changes. In other words, it is more sensitive to being slightly out of trim. Also, the nose attitude in level flight is relatively low in a Mooney compared to some other airplanes and this can cause a tendency to trim it too nose up. Cross checking with the attitude indicator will help with this. Another way to get the feel for proper trim if you have a 2-axis autopilot is to set power and put the autopilot in altitude hold and let it trim. Then disconnect the autopilot and manually move the trim wheel slightly each way to get the feel for finding the perfect trim again.

[PT20J]

On 8/22/2018 at 11:49 PM, jaylw314 said:

I'd avoid flying near best glide speed while IFR.  If you slow down below best glide, you'll start descending and slowing down more since you're on the back side of the power curve.

Best glide is C_L/C_D max speed. To get truly on the backside of the power curve, you have to be below the minimum power required speed where C_L^3/2/C_D  is maximum, which works out to 76% of the best glide speed (for a derivation of this, see Anderson, Aircraft Performance and Design, Chapter 5). That turns out to be pretty slow. For a Mooney (and most piston powered GA airplanes) the backside of the power curve isn't the big deal that it's been made out to be.

Skip

[jaylw314]

2 hours ago, PT20J said:

Best glide is C_L/C_D max speed. To get truly on the backside of the power curve, you have to be below the minimum power required speed where C_L^3/2/C_D  is maximum, which works out to 76% of the best glide speed (for a derivation of this, see Anderson, Aircraft Performance and Design, Chapter 5). That turns out to be pretty slow. For a Mooney (and most piston powered GA airplanes) the backside of the power curve isn't the big deal that it's been made out to be.

Skip

You're correct, that was incorrect use of the concept of "backside of the power curve."  It still doesn't change the fact that below best glide at low power settings, if you decrease speed, your angle of descent will decrease instead of increase, and it's your angle of descent that matters on a approach with vertical guidance

[PT20J]

11 hours ago, jaylw314 said:

You're correct, that was incorrect use of the concept of "backside of the power curve."  It still doesn't change the fact that below best glide at low power settings, if you decrease speed, your angle of descent will decrease instead of increase, and it's your angle of descent that matters on a approach with vertical guidance

Well, best glide is the speed that, power off, gives the minimum descent angle. Any speed, higher or lower, will result in a steeper descent. Low power isn't much different than power off.

[midlifeflyer]

On 12/21/2018 at 12:58 PM, Immelman said:

A property rigged mooney is a very stable IFR platform.

Incredibly stable. So much so, I even commented on it in my logbook. It was my first flight in actual (3.7 hours of it) in a C with a shotgun panel. My logbook entry notes that, even with the shotgun panel and no autopilot, it was "Stable easy to fly." My wife commented she felt like she was on an airline.

[midlifeflyer]

On 12/21/2018 at 1:16 PM, jaylw314 said:

If you are noticing what I noticed, I think it is because the Mooney is a low-drag airframe, so it takes TIME to get a stable airspeed and altitude.  Once you change either, it takes a relatively long time for those to stabilize because the power is so low for any given speed in level flight.  If you trained in anything like a C172 or Cherokee, you learned to apply some yoke pressure, then trim to relieve that pressure.  In the time it takes you to reach for the trim knob (or crank) and start trimming, those high-drag airframes have already stabilized.  I might suggest whenever you change attitude, count to 3 before you trim it out (or get used to trimming once, then trimming again a few seconds later).

Do you think your scanning also needs to pick up speed?  That might also be an explanation for problems holding altitude precisely?

Bingo. Staying ahead of a fast airplane with a lower drag profile starts earlier than staying ahead of an airplane with a higher drag profile.