Question about use of throttle during Lazy 8s

[Mac Ottlinger]

I have my commercial checkride in a few weeks. I'm feeling very confident about it, however I've had trouble with Lazy 8s. My first one to the right is usually well within the ACS standards, but on the second one to the left after my rollout, I tend to gain too much airspeed in the descent and bust the ACS airspeed standards. What I realized last week is that after setting the RPM in the 172 for the recommended entry speed of 105 knots and tightening up the throttle friction, the throttle still creeps in +100 RPM or so during the descent on my first lazy 8.

The way I was taught to perform the maneuver is to go straight into my second lazy 8 to the left after my first one to the right. However, based on my issue with my RPM increasing in the descent on my first lazy 8 to the right, would it be unreasonable on my checkride to decrease the RPM to it's original setting that I went into the maneuver with during rollout before I perform my second lazy 8 to the left? Would love to hear from some instructors or DPEs on this.

 

[dtuuri]

However, based on my issue with my RPM increasing in the descent on my first lazy 8 to the right, would it be unreasonable on my checkride to decrease the RPM to it's original setting that I went into the maneuver with during rollout before I perform my second lazy 8 to the left? Would love to hear from some instructors or DPEs on this.

Kudos to you for noticing the effect! I doubt whether anyone else on this forum besides you and me have ever made note. AND, I bet somebody will now argue about it! Think about it—most of the flying during a lazy 8 is at a reduced drag in comparison to entry drag, so either you'll gain airspeed or altitude. My cure is to reduce power slightly as you enter the first one, based on your trial and error experience. Don't even bother to mention it though, just a little secret between you and your airplane. EDIT: Your test will probably be at a higher gross weight, so consider how that may skew your power reduction.

 

[455 Bravo Uniform]

Not a CFI or DPE, nor Comm.

Question: do you hafta look at the tach for these maneuvers, or just give er what she needs?

 

[MauleSkinner]

Kudos to you for noticing the effect! I doubt whether anyone else on this forum besides you and me have ever made note. AND, I bet somebody will now argue about it! Think about it—most of the flying during a lazy 8 is at a reduced drag in comparison to entry drag, so either you'll gain airspeed or altitude. My cure is to reduce power slightly as you enter the first one, based on your trial and error experience. Don't even bother to mention it though, just a little secret between you and your airplane. EDIT: Your test will probably be at a higher gross weight, so consider how that may skew your power reduction.

You win the bet.

would not the initial pitch up and the recovery at the bottom of each half be at higher drag, compensating for the lower drag of the middle half? Maybe that’s why I find it works better with a bigger pitch change...I’m increasing the proportion of increased drag and reducing the proportion of decreased drag so that it balances out.

edit: Adjusting bank angle can change the Equation as well...from the AFH:
Power should be set so as not to enter the maneuver at an airspeed that would exceed manufacturer’s recommendations, which is generally no greater than VA. Power and bank angle have significant effect on the altitude gained or lost; if excess power is used for a given bank angle, altitude is gained at the completion of the maneuver; however, if insufficient power is used for a given bank angle, altitude is lost.

 

[dtuuri]

would not the initial pitch up and the recovery at the bottom of each half be at higher drag, compensating for the lower drag of the middle half? Maybe that’s why I find it works better with a bigger pitch change...I’m increasing the proportion of increased drag and reducing the proportion of decreased drag so that it balances out.

A fine question for the OP, a commercial applicant, to answer, citing empirical data he recorded himself of course.

 

[sarangan]

I have my commercial checkride in a few weeks. I'm feeling very confident about it, however I've had trouble with Lazy 8s. My first one to the right is usually well within the ACS standards, but on the second one to the left after my rollout, I tend to gain too much airspeed in the descent and bust the ACS airspeed standards. What I realized last week is that after setting the RPM in the 172 for the recommended entry speed of 105 knots and tightening up the throttle friction, the throttle still creeps in +100 RPM or so during the descent on my first lazy 8.

The way I was taught to perform the maneuver is to go straight into my second lazy 8 to the left after my first one to the right. However, based on my issue with my RPM increasing in the descent on my first lazy 8 to the right, would it be unreasonable on my checkride to decrease the RPM to it's original setting that I went into the maneuver with during rollout before I perform my second lazy 8 to the left? Would love to hear from some instructors or DPEs on this.

Its been years since I did or taught a lazy 8, but I am glad to hear you are diving into the details. When you say throttle creeps, is this because the friction lock on the throttle knob isn't holding, or are you referring to the increase in RPM due to the increase in airspeed (assuming fixed pitch prop)?

 

[dmspilot]

the throttle still creeps in +100 RPM or so during the descent on my first lazy 8.

Does it? Is there another reason why the RPM would increase in a descent?

 

[Mac Ottlinger]

Does it? Is there another reason why the RPM would increase in a descent?

Should have mentioned the aircraft is a 172S. Not using an RG since they got rid of the complex requirement for the commercial checkride. I'm aware though of the increase in RPM with a fixed pitch propeller in a descent due to the increase in airspeed, which if I remember correctly results in less drag because the increased airspeed decreases the angle of attack of the propeller blades. Not sure if I'm correct on that statement though if somebody could confirm or correct that.

 

[Mac Ottlinger]

Its been years since I did or taught a lazy 8, but I am glad to hear you are diving into the details. When you say throttle creeps, is this because the friction lock on the throttle knob isn't holding, or are you referring to the increase in RPM due to the increase in airspeed (assuming fixed pitch prop)?

What I noticed last time I ran through the maneuver is that the RPM never dropped leveling/rolling out between each turn. Even with the friction locked down tight it seems like the throttle creeped forward somewhat and the lock wasn't holding. Wouldn't surprise me if it's just due to the fact that the aircraft I fly is a trainer with thousands of hours on it. CAn't expect the friction lock to work like it did fresh out of the factory.

 

[Boone]

Should have mentioned the aircraft is a 172S. Not using an RG since they got rid of the complex requirement for the commercial checkride. I'm aware though of the increase in RPM with a fixed pitch propeller in a descent due to the increase in airspeed, which if I remember correctly results in less drag because the increased airspeed decreases the angle of attack of the propeller blades. Not sure if I'm correct on that statement though if somebody could confirm or correct that.

That may be true but I think time spent closer to L/D max would have more of an effect on total drag than the prop. My guess is more time is spent slower, which is closer to L/D max and more efficient.

 

[6612v]

Don't over think it. The examiner will be looking to see if you are maintaining a constant radius by adjusting your ground speed with pitch maintaining proper rudder control. Put power at 24, keep hand on throttle while pinching the stem so it doesn't slide, and concentrate on the maneuver. Its all about aircraft control and coordination, no power adjustments necessary.

 

[dtuuri]

Don't over think it. The examiner will be looking to see if you are maintaining a constant radius...

I hope not. Maybe you're thinking of a different kind of "8"? This would be a crazy 8.

 

[brcase]

Seems unlikely to me that the thottle is only creeping during lazy eights. Does it creep during cruise?

You may find that your stable cruise setting for 105 is different than the power setting you need to perform consecutive Lazy 8’s. My guess is you should probably reduce your power slightly as you enter The pull up into the 1st 45 degrees.

You also need to evaulate how slow you are getting at the top of each eight and how much altitude you are gaining. Too fast at the bottom can be caused by not slowing down enough at the top or also be pitching down to fast between the 90 and 135 point (especially closer to the 90 degree side). As the plane accelerates to quickly which reduces the turn rate. Rolling out to quickly just past the 90 degree point can contribute as well as you don’t get turned fast enough. Often between the 90 and 100 degree point you will have no less than 25 degrees bank.

A lot of figuring out lazy 8’s is that way at you do now affect what the plane is going to do 45-90 degrees later in the turn.

Brian
CFIIG/ASEL

 

[denverpilot]

Anytime I found the airspeed at the bottom of a lazy 8 was too high, the person (including me) performing it was forcing the nose down at the top.

If you get properly slowed enough at the top, the nose will fall through by itself and maybe even require a tad more back pressure to arrest it as it “slices” through the horizon.

105 sounds a bit fast for entry in a Skyhawk to me, but one can certainly play with it unless that’s some number mentioned in a newer Skyhawk ACS or something. If it is, the initial entry probably isn’t steep enough on the way up and you’re not slow enough when you “lazily” let the nose fall through.

It’s literally a lazy maneuver. But you do have to play with initial pitch and bank to get the aircraft truly slow at the top. Like sloppy control slow is the sweet spot. Then just adjust for all the turning tendencies with rudder depending on direction and help it smoothly transition without the nose flopping down or a wing dropping off... and it’ll come around the corner on its own.

Seems to be the common thread is get the entry right and work the rudder as it slows and the aircraft will do most of the maneuver for you. Slowly. Be patient.

 

[MauleSkinner]

Seems to be the common thread is get the entry right and work the rudder as it slows and the aircraft will do most of the maneuver for you. Slowly. Be patient.

If you’re touching the yoke/stick for more that 25% of the maneuver, you’re working too hard.

 

[midlifeflyer]

I love this Lazy 8 demo by Jason Miller.

 

[midlifeflyer]

the throttle still creeps in +100 RPM

Not really. You are flying a fixed pitch prop. When you climb or descend you are changing the prop pitch (AoA) relative to the airflow. The result without moving the throttle is an increase in RPM in a descent and decrease in RPM in a climb.

 

[Maxnr]

Just asking, are you using a reference point too close? I was taught to pick out something on or near the horizon. At 3.000' the maneuver is rather gentle or "lazy" due to the distance from the r.p. I still enjoy lazy eights years after I had the cert in my pocket. But over the years, when I didn't have to do them according to the ACS, I chose a reference point much closer and that made them much more "sporty". I never touch the power during the maneuver. I have done them in airplanes with fixed pitch props, C.S. props, helicopters and gliders. All fun. More fun if the r.p. is less than 5 miles away at about 5,000'.

 

[Salty]

I love this Lazy 8 demo by Jason Miller.

That video frustrates me because he talks about how you only have to time the pull and when to let go and then never actually tells you how to time letting it go.

 

[MauleSkinner]

Just asking, are you using a reference point too close? I was taught to pick out something on or near the horizon. At 3.000' the maneuver is rather gentle or "lazy" due to the distance from the r.p. I still enjoy lazy eights years after I had the cert in my pocket. But over the years, when I didn't have to do them according to the ACS, I chose a reference point much closer and that made them much more "sporty". I never touch the power during the maneuver. I have done them in airplanes with fixed pitch props, C.S. props, helicopters and gliders. All fun. More fun if the r.p. is less than 5 miles away at about 5,000'.

Isn’t the reference point the horizon?

 

[Tokirbymd]

If you’re touching the yoke/stick for more that 25% of the maneuver, you’re working too hard.

How can you do this? If I trim for level flight at entry the whole rest of the maneuver is out of trim and applying a buttload of back pressure, no?

 

[MauleSkinner]

How can you do this? If I trim for level flight at entry the whole rest of the maneuver is out of trim and applying a buttload of back pressure, no?

No...you pull to the 45-degree point and let the trim do the rest on each half of the maneuver. The bank makes it work.

 

[denverpilot]

How can you do this? If I trim for level flight at entry the whole rest of the maneuver is out of trim and applying a buttload of back pressure, no?

Keep trimming. Heh.

He’s not saying it doesn’t change. It just doesn’t require yoke or stick man-handling.

It’s thhhaaaaaaaaat sllllloooooooooooowwww and slow subtle movements.

I kinda have to work harder at the top in the R/STOL 182 because getting near the stall is pretty much just a jumble of propwash and controls that almost aren’t working, but in anything without stall fences or vortex generators or droop tips or anything, there’s still airflow over the controls.

But I can pretty much just nudge the yoke and rudder to start and keep trimmed for the vast majority of it. Just have to think a tad about rudder to give enough of it to the right like any slow maneuver. Left it kinda handles itself but wants to over bank.

I think a lot of people choose ground reference points too close together and force it to be higher bank than it needs to be. Sometimes it’s better to demo it without trying to hit any ground reference point other than crossing a line and letting the first few show you how wide and big the thing can be. Just note where you cross the line without trying to keep it to a particular radius. Then you can play with more or less bank and more or less nose up to start to see if you get the relationships between all the forces like the rudder needed and the overbanking tendency at the top and all of that.

It’s just a big slow symmetrical swoop where you’re keeping all the stuff fighting the airplane from making it uncoordinated and symmetrical but the airplane is very close to doing it all on its own.

Talking through it helps. “Slowing down so oberbanking is starting so aileron against that, let off a little rudder the nose is coming around too quickly (left) as we slow...” etc.

I tried to do them more like low level ground reference maneuvers at first which was a mistake. I wanted to roll out to fly over “that tree” or “that intersection” or whatever.

It’s kinda “more zen” than that. Engineer brain fought that for a bit. Ha. Just fly a big smooth turn and check how it’s going at the checkpoints.

 

[midlifeflyer]

That video frustrates me because he talks about how you only have to time the pull and when to let go and then never actually tells you how to time letting it go.

Out of curiosity, I've done it using his method in a completely different airplane. Letting go requires situational awareness and knowledge of how the airplane responds. He's not teaching a "close your eyes" method,

 

[eman1200]

anyone else just do these over a road and not use ref points on the horizon? anyone else not find this maneuver overly difficult?

 

[MauleSkinner]

anyone else just do these over a road and not use ref points on the horizon? anyone else not find this maneuver overly difficult?

It’s like tailwheel flying, NDBs, etc...somebody told us it was hard before we started.

 

[Maxnr]

Isn’t the reference point the horizon?

When I was a student pilot in Maine, I was told to use Mount Washington almost a hundred miles away-----On the horizon. When you start, the reference POINT is n one side. When you return to level, 180 deg change of direction, the reference POINT is on the other side.
My instructor was a former Embry Riddle military contract instructor. I got lazy 8's and chandels just after solo. 7.8 hrs.

 

[Tokirbymd]

Keep trimming. Heh.

He’s not saying it doesn’t change. It just doesn’t require yoke or stick man-handling.

It’s thhhaaaaaaaaat sllllloooooooooooowwww and slow subtle movements.

I kinda have to work harder at the top in the R/STOL 182 because getting near the stall is pretty much just a jumble of propwash and controls that almost aren’t working, but in anything without stall fences or vortex generators or droop tips or anything, there’s still airflow over the controls.

But I can pretty much just nudge the yoke and rudder to start and keep trimmed for the vast majority of it. Just have to think a tad about rudder to give enough of it to the right like any slow maneuver. Left it kinda handles itself but wants to over bank.

I think a lot of people choose ground reference points too close together and force it to be higher bank than it needs to be. Sometimes it’s better to demo it without trying to hit any ground reference point other than crossing a line and letting the first few show you how wide and big the thing can be. Just note where you cross the line without trying to keep it to a particular radius. Then you can play with more or less bank and more or less nose up to start to see if you get the relationships between all the forces like the rudder needed and the overbanking tendency at the top and all of that.

It’s just a big slow symmetrical swoop where you’re keeping all the stuff fighting the airplane from making it uncoordinated and symmetrical but the airplane is very close to doing it all on its own.

Talking through it helps. “Slowing down so oberbanking is starting so aileron against that, let off a little rudder the nose is coming around too quickly (left) as we slow...” etc.

I tried to do them more like low level ground reference maneuvers at first which was a mistake. I wanted to roll out to fly over “that tree” or “that intersection” or whatever.

It’s kinda “more zen” than that. Engineer brain fought that for a bit. Ha. Just fly a big smooth turn and check how it’s going at the checkpoints.

Hmm, ok maybe I'm overcontrolling it then. My CFI that showed them to me intially had me climbing pretty steep with 45deg bank at the max as that was how he did them before the ACS change. I have been muscling it to meet the parameters at the correct 45/90/135 etc points but didn't feel very elegant.

 

[MauleSkinner]

Hmm, ok maybe I'm overcontrolling it then. My CFI that showed them to me intially had me climbing pretty steep with 45deg bank at the max as that was how he did them before the ACS change. I have been muscling it to meet the parameters at the correct 45/90/135 etc points but didn't feel very elegant.

I started people out at 45-60 degrees of bank-they’re actually easier, IMO-and then backed them down to 30.

get it to the proper 45-degree point and let go of the yoke for the next 135, and see where you end up. It’ll probably just take minor nudges to perfect them. (Assuming the airplane flies reasonably straight hands-off to start with)

 

[EdFred]

Lazy 8, not Workaholic 8.

Pull and bank to start maneuver, let the stability of the plane do the rest of it.

Maybe we should call them Millennial Eights.

 

[denverpilot]

Lazy 8, not Workaholic 8.

Ed wins favorite internet comment of the day from me! Truly laughed at that.

 

[midlifeflyer]

Hmm, ok maybe I'm overcontrolling it then..... I have been muscling it to meet the parameters at the correct 45/90/135 etc points but didn't feel very elegant.

That sounds like a good self-assessment. As a number have pointed out muscling is not required.

 

[Kenny Phillips]

When I was a student pilot in Maine, I was told to use Mount Washington almost a hundred miles away-----On the horizon. When you start, the reference POINT is n one side. When you return to level, 180 deg change of direction, the reference POINT is on the other side.
My instructor was a former Embry Riddle military contract instructor. I got lazy 8's and chandels just after solo. 7.8 hrs.

Yeah, we did all the commercial maneuvers early in training, as well. I think that it made learning them easier.

 

[labbadabba]

Anytime I found the airspeed at the bottom of a lazy 8 was too high, the person (including me) performing it was forcing the nose down at the top.

If you get properly slowed enough at the top, the nose will fall through by itself and maybe even require a tad more back pressure to arrest it as it “slices” through the horizon.

105 sounds a bit fast for entry in a Skyhawk to me, but one can certainly play with it unless that’s some number mentioned in a newer Skyhawk ACS or something. If it is, the initial entry probably isn’t steep enough on the way up and you’re not slow enough when you “lazily” let the nose fall through.

This. As the weather gets cooler performance will increase too. I find my pitch up in cooler weather doing Lazy 8s is more pronounced to find that break. The Finer Points YouTube channel has an excellent demonstration on Lazy 8s. But in terms of power, I usually do them at 2300 rpm in a 172 which is about 105KIAS in level flight which is right a Vma, I feel like this is usually the sweet spot for most of the commercial stuff.