8's on Pylons - Power Adjustment

Discussion in 'Pilot Training' started by labbadabba, May 28, 2019.

  1. labbadabba

    labbadabba Pattern Altitude

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    Practiced some 8's on Pylons in rather windy conditions (220 at 30kts) this weekend and had a terrible time. One thing that I noticed, as I turned to the upwind side, I really had to drop my altitude to keep the pylon. However, this big push on the nose really increased the RPM on the motor (I did the maneuver at about 2200 RPM in a C172M). In other words, my groundspeed was decreasing so my pivotal altitude was dropping so I had to descend. Due to the wind, the loss of groundspeed was so rapid that I really had to dive. This caused me to pick up speed again in the dive and the engine speeding up to 2500+ RPM. I was really fighting the maneuver the whole way.

    So to keep my altitude more stable, I began to pull back a touch of power as I pitched down to keep my airspeed more constant and again on the downwind side where I had to climb slightly I added a bit of thrust to maintain airspeed.

    When I was taught 8's on Pylons I was told not to touch the power because it will jack with your pivotal altitude but I'm wondering if in this case, due to the high winds is adjusting the power is warranted?
     
  2. bluesideup

    bluesideup Pre-takeoff checklist

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    Hi.
    At 30 kts they can be difficult but doable if:
    You enter at the Maneuvering speed with the wind behind you / downwind where the steepest turns are required.
    Enter at he the proper altitude.
    It's very important that you stay ahead of the acft and you anticipate the change otherwise you will will be chasing it.
    Speed is not an element that is required to be maintained as long as you keep the proper distance from the pylons and you can still fly / control the acft. and you should not have to change the power / RPM if done properly.
    If you enter at ~99 KIAS you should still be able to control it.
     
  3. apr911

    apr911 Pre-takeoff checklist

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    With that much headwind, the higher RPM is not going to result in a noticeably increased speed if you leave it but the concern would be overspeeding the prop/engine above redline.

    Trying to do any training maneuver in 30kt winds, especially low level maneuvers, seems a bit foolhardy to me.

    The book doesnt specify a minimum or maximum wind speed for eights on pylons however, the Airplane Flying Handbook does publish a chart for pivotal altitudes with groundspeeds between 87 and 113 kts. While you can absolutely calculate the pivotal altitudes for higher/lower airspeeds, to me this chart indicates the sweet spot is 100kias with a maximum of 13 kt winds.

    Especially in the typical trainer where faster airspeeds aren't possible without being full power and surpassing redline on the upwind portion, I certainly wouldn't fly them above around 15-20kts... Even setting a lower power/speed puts you at an unacceptably low altitude.

    Downwind the turn bank angle should be the same as in the upwind for Eights ON Pylons; the bank angle does not change in the maneuver. While the ACS does not specify to maintain an airspeed (or groundspeed), the maneuver is significantly more difficult when you vary the airspeed.

    At 99kias, during the upwind portion they are looking at a ground speed of 69kts and a pivotal altitude of 420ft which is almost certainly a violation of 91.119 inmost areas. On the downwind, they're looking at 129kts groundspeed and a 1472ft pivotal altitude...

    That represents a change of 1050ft over a maneuver that typically would be no more than a 3 or 4 minutes total and you would have 3 of these changes over the course of the manuever.
     
    Last edited: May 28, 2019
  4. labbadabba

    labbadabba Pattern Altitude

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    The overspeed is what I was encountering for sure. We've had nothing but brutal winds since January here on the few flyable days we've had. It's been an absolutely awful stretch of weather. Even if surface winds are relatively calm we always seem to have a LLJet in the area.
     
  5. dtuuri

    dtuuri En-Route

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    Backwards. You need to keep your groundspeed more stable not your airspeed. That's why you have to dive, so IAS increases and raises your pivotal altitude. The other way around (reduce IAS) when going downwind.
     
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  6. labbadabba

    labbadabba Pattern Altitude

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    Right, I think my issue was, there was a 60kt difference in groundspeed between the upwind and downwind legs. To account for this, I really had to dive the nose down but this in turn also increased my IAS and my RPMs. I think the lesson here really is, don't do 8's on Pylons in 30kt winds...
     
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  7. mondtster

    mondtster En-Route

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    In my opinion, that was the correct lesson to learn. All the experienced instructors in my area cut off the maneuver when the winds are being reported at over 20 knots due to the significant differences in pivotal altitude as the ground speed changes. Having a somewhat local stall/spin accident in high winds that killed a student and instructor is probably an influence on our decisions as well.
     
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  8. apr911

    apr911 Pre-takeoff checklist

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    Had to read this post several times before it made sense what was being said but I agree with dtuuri, your airspeed should normally be stable throughout the maneuver. In your case with the 30kt headwind, you'd want to dive and try to increase IAS which comes with an associated increase in groundspeed and therefore increased pivotal altitude (since pivotal altitude is calculated using groundspeed not IAS... I think that's what threw me off with dtuuri's post, that and stabilizing groundspeed which I realized was meant in more relative terms).

    On the downwind, with a 30kt tailwind, in order to slow your groundspeed enough to make a enough of a difference in most aircraft, you'd have to further decrease power and get uncomfortably close to Vs1 stall speeds in a clean configuration at a very low altitude and in a turn with a natural tendency/common error to fly uncoordinated in an effort to correct the pylon's position on the wing tip. This is a recipe for a stall and not the gentle-fly-the-stall type of stall but a sudden incipient spin and abrupt loss of altitude type of stall that would have catastrophic results at the low mostly sub-1000ft altitudes required for the maneuver.
     
  9. labbadabba

    labbadabba Pattern Altitude

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    Glad I'm not dead.
     
  10. ja_user

    ja_user Pattern Altitude

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    I've never paid attention to altitude or groundspeed (other than entry) during this manuever. You just keep the pylon in the same point on the wing, and it works itself out. And I've done it many times from Calm to 30kt winds.
     
  11. Kritchlow

    Kritchlow Final Approach

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    Not sure I’ve ever done one successfully.
    Well, I guess I did (lucked out) twice. Once on my sign off ride and once on my CP ride.

    I’m certain I could not duplicate that today.
     
  12. dtuuri

    dtuuri En-Route

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    They are sooo hard. Actually, I think they should just do on-pylons and forget about the eights. Or at least let the applicant pick the second pylon at the place the wing is banked the other way—just use whatever it points at (and hope you can find it again).
     
  13. ja_user

    ja_user Pattern Altitude

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    You Serious Clark?
     
  14. Kritchlow

    Kritchlow Final Approach

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    I’m not Clark, but I remember 1986?) when I did commercial and there was 8’s on and 8’s around pylons.
    Is that still the case?

    I’m one of the few here that actually found commercial maneuvers hard. Perhaps that is a function of the standard you were expected to do the maneuvers. I totally get the whole ACS thing, but back then things had more discretion... in both directions.

    I also remember “steep power turns” and “steep spirals”.
    No clue if that’s still a thing.
     
  15. mondtster

    mondtster En-Route

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    8s around pylons are not in the current commercial ACS, nor have they been in the PTS for a while now. I'm not sure when they were removed.

    Even now, to perform the typical commercial maneuvers well can be challenging. I'd venture to guess that many of the people who think they're easy have low standards on their airmanship skills. The standards which are considered passable by the ACS and most DPEs are substandard in my book.

    Steep turns and steep spirals are both performance maneuvers that remain in the ACS.
     
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  16. dtuuri

    dtuuri En-Route

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    I'm not Clark, but yes I'm serious. To start with, the real world application of the maneuver is to orbit something on the ground without need of taking your eyes off of it. You also have to compensate for the full effects of wind during 360°. The eight on pylon breaks you off into level flight too soon. The "eight" places too much emphasis on selecting pylons, which can be "mission impossible". Here's a few choice words plucked from the AFH to back me up:

    "The eights-on-pylons is the most advanced and difficult of
    the ground reference maneuvers. Because of the techniques
    involved, the eights-on-pylons are unmatched for developing
    intuitive control of the airplane.
    ...
    Selecting proper pylon is an important factor of successfully
    performing eights-on-pylons. They should be sufficiently
    prominent so the pilot can view them when completing the
    turn around one pylon and heading for the next. They should
    also be adequately spaced to provide time for planning the
    turns but not spaced so far apart that they cause unnecessary
    straight-and-level flight between the pylons. The selected
    pylons should also be at the same elevation, since differences
    of over few feet necessitate climbing or descending between
    each turn. The pilot should select two pylons along a line that
    lies perpendicular to the direction of the wind. The distance
    between the pylons should allow for the straight-and-level
    flight segment to last from 3 to 5 seconds."​
     
  17. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    That's the secret my CFI instructor taught me. Pick the first pylon. The second is whatever is there when you dip the wing the other way.
     
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  18. apr911

    apr911 Pre-takeoff checklist

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    I admit that I found the commercial maneuvers more difficult than expected. Steep spirals and steep turns weren't a big deal and the mechanics behind the lazy-8s and chandelles weren't difficult but I had individual performance struggles with both (was too aggressive/impatient and wanted to do wingovers for lazy-8's and a tendency to struggle to hold enough back pressure as the plane slowed, momentarily dropping the nose a bit resulting in higher exit speeds in chandelles).

    8's around pylons weren't required for my CPL but they dont look that difficult, just turns around a point in opposite directions (which we normally at least train for in PPL). The only "complicated" part is linking them together.

    8's on pylons took the most instruction but that was more due to poor pylon selection than inability to perform the maneuver correctly. It was another CFI who finally gave me the pointers I needed to be able to perform the maneuver correctly.

    That's what I did on both my CPL and CFI checkrides with different DPEs for each, neither DPE had an issue with it. I picked my first pylon, made a "close enough" guess/estimate for the second and then revised accordingly once I dropped my wing.

    My CFI also taught me to pick 3 or 4 pylons. The first pylon was always to be the one used but the 2nd/3rd/4th should be pylons in a relatively straight line for use as the second pylon. The basic idea being that I should choose an area for my second pylon with extra pylons available so that when you drop the wing in the opposite direction, there is a reasonable chance of there being something prominent right on the wingtip (or close enough to it). If there is only 1 pylon out in the area where you plan to make the second turn, chances are when you drop the wing you wont have a prominent enough point available for the second turn.

    It should also be noted that the maneuver while designed to be able to be repeatable, only has to be flown once with a turn in either direction. Most of the time when training to help grasp the concept we fly the maneuver multiple times which increases the need for identifiable pylons but on a checkride, the DPE is likely to only have you fly one turn around each pylon.

    The emphasis in the AFH isn't "inaccurate," proper pylon selection is necessary for successful completion of the maneuver however, the passage could be simplified greatly. The passage also would lead most to believe that both pylons need to be selected before entering the maneuver.

    FWIW, the eights on pylons are still a bad real world maneuver. I cant think of a scenario in which you'd want to orbit 2 objects and only orbit them for 270 degrees at a time AND change the direction of your turn while doing it. The better scenario imo would be "turns/circles on pylons" (or whatever you want to call it). A 360 (or more) on a pylon to the left and then a 360 (or more) on a pylon to the right as "separate" maneuvers, that'd be more realistic.

    Also... in case you missed the reference.
     
    Last edited: May 31, 2019
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  19. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    We can get too crazy looking a "pylon." I remember the last time I was giving tips to a pilot doing them. It got to a point where I would say, "dip your wing, what do you see?" and the answer was "that yellowish spot on the ground." And they used that.

    Here's where I did my commercial and CFI rides

    upload_2019-5-31_14-55-27.png
     
  20. mondtster

    mondtster En-Route

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    Many students seem to have trouble with figuring out where the wind is coming from and selecting proper pylons. I wholeheartedly disagree with the posters in this thread suggesting that a second pylon isn't necessary or to wait and select the second pylon after going around the first one. To me, that demonstrates that the student doesn't have adequate understanding of the performance of the airplane they're flying and/or they aren't flying the maneuver consistently.

    People need to purge the idea that flight test maneuvers must have a real world application. They're a maneuver to test an applicant's airmanship and they do a pretty good job of it. Once a person is in that mindset they can focus on the task at hand.
     
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  21. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    Perhaps obvious that I disagree. Here's what the AFM says about selection:
    They should also be adequately spaced to provide time for planning the turns but not spaced so far apart that they cause unnecessary straight-and-level flight between the pylons. The selected pylons should also be at the same elevation, since differences of over few feet necessitate climbing or descending between each turn. The pilot should select two pylons along a line that lies perpendicular to the direction of the wind. The distance between the pylons should allow for the straight-and-level flight segment to last from 3 to 5 seconds.​
    That absolutely requires proper selection of two pylons but it does not require advance selection of both pylons. Do your first pylon turn, fly those 3-5 second and dip the wing. You have satisfied the selection criterion and you will be flying the maneuver very consistently since your selection of the second pylon took the actual wind conditions into consideration. And since it's reality-based, it's repeatable. If you would not be able to repeat it with a second turn around the first pylon and the around the second, to quote you, "To me, that demonstrates that the student doesn't have adequate understanding of the performance of the airplane they're flying and/or they aren't flying the maneuver consistently".

    Of course, I readily acknowledge there are some super-anal DPEs around too.
     
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  22. mondtster

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    My opinion is that waiting to define the second pylon is often (but not always) used as a crutch to try and hide when the maneuver isn’t going as planned. After flying the maneuver in a specific airplane type a few times you should be able to gauge the performance of the plane well enough to know how far the pylons need to be spaced and both pylons can be selected prior to entry.
     
  23. apr911

    apr911 Pre-takeoff checklist

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    Eight's on Pylons are a ground reference maneuver, not a performance maneuver.

    That would require you to have flown in all possible wind conditions. If your pylons are not perfectly perpendicular to the wind, your pylons will change. If the wind is variable in direction or speed and/or gust factor, your pylons will change. If your power/trim/airspeed is not perfectly set the same, your pylons will change. If your turn is not to the same degree of bank (which is itself, often somewhat dependent on the previous variables), your pylons will change. Heck even density altitude can even play a part in creating situations where performance and pylons will differ.

    I'd also note that while the recommended and expected procedure on a checkride is to select two pylons along a line that lies perpendicular to the direction of the wind and that pilots enter crosswind, it does not have to be done this way and unlike other ground reference maneuvers, you are maintaining the same amount of bank whether downwind or into the wind. The ACS only says that the pylons must be far enough apart to allow for straight and level flight between the pylons.

    The ACS is primarily concerned with the use of pivotal altitude to maintain the line-of-site reference on the pylon remains in the correct position and that you are able to divide your attention.


    I disagree that we should purge the idea. The FAA is all about Scenario-Based Training lately so while the maneuvers dont have to have a real world application they should have applicable scenarios of usage behind them whenever possible. Besides, pretty much every ground reference maneuver or performance maneuver in the airplane flying handbook has (or easily could have with a slight modification) a real world application; the only exception I can come up with is the various 8's and even within that, lazy-8's are the only one that I cant really think of an applicable real world application of the maneuver.
     
  24. mondtster

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    Nobody implied they weren't.
     
  25. dtuuri

    dtuuri En-Route

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    The bank varies with respect to the wind the same as a turn around a point; the radius changes because there's no wind correction applied.
     
  26. TRocket

    TRocket Line Up and Wait

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    Obviously in a calm wind situation power changes are not required. When I did them for my commercial I found that small power adjustments to supplement altitude changes came in very handy when winds had a noticeable effect on ground speed. I know some people are taught to not make power changes but I found them pretty useful