I think I'm over-rotating. Thoughts?

Discussion in 'Pilot Training' started by BocaFlyer, Mar 14, 2021.

  1. mondtster

    mondtster En-Route

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    That is likely the difference. Despite being largely the same airplane there are a couple significant differences between a Cherokee 140 and an Archer. First is wing design, second is stabilator dimensions. The archer flys largely like a skyhawk, the cherokee 140 does not. Airplanes fly like airplanes, but there are some subtle differences that you'll need to learn as you transition from one to another. The more types you fly the easier the transitions become.
     
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  2. Will Kumley

    Will Kumley Pre-takeoff checklist

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    Thats a great point. Wouldn't be hard at all to incorporate that.
     
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  3. BocaFlyer

    BocaFlyer Filing Flight Plan

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    And the case of 'slight nose up trim' would then be a turn or two aft from the middle, I presume?
     
  4. David Megginson

    David Megginson Cleared for Takeoff

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    Trial and error. :)
     
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  5. BocaFlyer

    BocaFlyer Filing Flight Plan

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    :eek:
     
  6. kgruber

    kgruber En-Route

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    On the Dassault I flew, takeoff trim was part of the after landing checklist. There have been mis-trimmed jets that can't "rotate" and have gone into the pucker brush. Pilots make mistakes, and the more backup checklists.......the better.
     
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  7. Divine Wind

    Divine Wind Pre-Flight

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    Lots of good tips here so I won't recover them and will only ask this: how much time have you had with another Piper pilot? Ask them or go up with one.

    There are rules and recommendations and there are techniques. Techniques are not required and don't work for everyone.

    In the case of flying a new or relatively new aircraft, my technique is to give it as much respect as possible. Basic rules apply: Airspeed is life and Altitude is your friend. The three most useless things in aviation are runway behind you, altitude above you and fuel that's still in the truck.

    As others suggested, check your W&B and trim wheel settings. BTW, mechanics have been known to make mistakes including mistrimming aircraft which is why you check the trim setting then look at the trip tab.

    In your situation, I'd put the plane on the numbers as close to the threshold as possible, complete run up, hold the brakes, run the power up and then let it go. You should be able to feel when the aircraft wants to fly as the nose wheel gets light, but my technique for a new plane is to hold the nose down for a few more seconds to let more Bernoullis flow over the wing. Rotating 10 knots fast is generally a good thing. In fact being fast for everything except running into something is good rule of thumb.
     
  8. BocaFlyer

    BocaFlyer Filing Flight Plan

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    Only on my checkout in the tapered-wing Archer. This is definitely the best advice though, I think.

    Question on this: when the trim wheel is in the middle (say after 5 rolls if it's 10 rolls from full fore to aft) should the trim tab be aligned with the stabilator? I presume that's where the neutral trim would be (not deflected either up or down and thus having no impact)
     
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  9. David Megginson

    David Megginson Cleared for Takeoff

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    The challenge is that the Piper stabilator trim tab doubles as a stabilator antiservo tab (which is very clever), so it moves relative to the stabilator as you move the stabilator up and down.
     
  10. A1Topgun

    A1Topgun Line Up and Wait

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    If you leaned "attitude flying" from the get-go it is a lot easier to transition into different A/C. Also, good idea to do some Dutch Rolls "Wiggle your wings" to get a feel of rudder/aileron co-ordination.
     
  11. Divine Wind

    Divine Wind Pre-Flight

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    Switching planes is fun, but has a learning curve.

    If a person is used to a sports car and goes speeding down a curvy road, that might be fine but if they try it in an SUV, they could end up in the weeds. Pipers are great airplanes and good flyers but switching from high wing to low wing or vice versa is a transition process that can't be covered in a 30 minute brief. A little training and a lot of questions like you're asking is a safe way to start out.

    The manual should say the wheel setting and the preflight manual might say what to look for. A CFI or Piper pilot can tell you. Individual planes can have idiosyncrasies too which FBO's or the owner should know about.
     
  12. David Megginson

    David Megginson Cleared for Takeoff

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    There's not much difference among trainer-level Piper and Cessna nosedraggers, IMO. There are specifics to learn, like V-speeds, approach flaps, etc—and you can spend your whole life learning to appreciate the finer points of any aircraft—but they're all docile and handle similarly enough. I suspect it's when you step up to complex/high-performance/multiengine that the differences among models are big enough to need more than a short familiarisation flight before you start learning on your own.
     
  13. SoCal RV Flyer

    SoCal RV Flyer En-Route

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    With the RV-9A I "rotate" at about 30 KIAS and hold the nose wheel off the runway about 6"; at this attitude the aircraft will fly itself off (Takeoff-o-Matic? :)) at a little over 60 knots. Or I can tug back on the stick a little right at 60. Pretty much SOP for a Van's trike gear, and possible because of light nose wheel loading, lots of elevator area and generous throw.
     
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  14. Kritchlow

    Kritchlow Final Approach

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    Interesting. Most Jets I have flown the takeoff trim setting depended on weight & CG. In many it was a setting for a V1 failure, so the airplane was in trim for an emergency.
     
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  15. Domenick

    Domenick Line Up and Wait

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    Very early in my flying I had that experience in my Warrior and it scared the shlt out of me. Trim was far nose down from the last flight. Not sure if the last flight was me or my plane partner, but it's on me for forgetting to check trim position during preflight. Home drome is 2600 feet long with a 25' power line 100' from the end I was pointed at. The plane would not liftoff. About halfway, I horsed it into the air and she barely climbed. Turned out before the end and scooted between a gap in the trees (now removed). The yoke was nearly pinned back to its stop. I called an emergency, and made a very low pattern with a lot of back pressure holding her in the air. Landed. Soon found the trim issue. Made the flight.

    Yes, I should have aborted the takeoff. I didn't. Yes, I should have found the issue in the air. I didn't. I learned a very important lesson which I have never forgotten. And "Set neutral trim" is now on my post-flight checklist. That experience and turbulence on Maui were my two scariest flying moments.
     
    Last edited: Mar 16, 2021
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  16. David Megginson

    David Megginson Cleared for Takeoff

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    The trim tab on the PA-28's stabilator also acts as an anti-servo tab so that it's difficult to move too far past the trimmed position; otherwise, I think that huge moving stabilator (compared to the small hinged elevator in a Cessna 172) would make it too easy for the pilot to snap the nose up rapidly into a deep stall (just speculation).
     
  17. David Megginson

    David Megginson Cleared for Takeoff

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    The trim tab on the PA-28's stabilator also acts as an anti-servo tab so that it's difficult to move too far past the trimmed position; otherwise, I think that huge moving stabilator (compared to the small hinged elevator in a Cessna 172) would make it too easy for the pilot to snap the nose up rapidly into a deep stall (just speculation). I can imagine you'd almost need both hands on the yoke and your feet braced against the panel to pull the yoke back to takeoff position when it was trimmed so far forward.

    Sadly, that's similar to the situation the 737 MAX pilots faced with the MCAS runaway, except that in two cases they weren't able to overpower it.
     
  18. woodchucker

    woodchucker Pattern Altitude

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    I too was just checked out in a Cherokee not long ago. Having only made two takeoffs from a full stop I noticed the same thing. I’ll have to try some of the ideas mentioned here next time up.

    I also fly a Tiger and do not feel the same “heavy control” feeling on takeoff though. Maybe it’s just a matter of experience in the aircraft.
     
  19. Domenick

    Domenick Line Up and Wait

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    If by "anti-servo" you are referring to an auto-pilot, I have none.
     
  20. David Megginson

    David Megginson Cleared for Takeoff

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    No, I mean that it exerts pressure in the opposite direction on the stabilator when you're trying to move it away from its trimmed position (and the pressure increase the further you pull or push it).

    An elevator will do that anyway — it's part of the basic pitch stability of a conventional airplane — but with the big, all-moving stabilator on the PA-28, Piper must have decided it needed a little help to discourage a fast pull into a deep stalls at in slow flight (where there's less resistance).
     
    Last edited: Mar 20, 2021
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  21. Divine Wind

    Divine Wind Pre-Flight

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    Agreed. Mistrimmed aircraft have contributed many mishaps. A few fatal. Mostly just pilots in the weeds trying to get their story straight. :)

    The USAir Flight 5050 crash was due to mistrim. Hence the "USAIR means underwater seating available in rear" joke.
     
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  22. Divine Wind

    Divine Wind Pre-Flight

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    Sometimes that's maintenance. If your experience is one airplane, hard to tell. If it's many of the same type and it feels that way, then, yes, it's the aircraft.

    I've never had the pleasure of flying a Grumman Tiger....or any Grumman for that matter. Never had the option.
     
  23. Divine Wind

    Divine Wind Pre-Flight

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    Same for any airplane. Some are more forgiving than others. Then there's accidents due to maintenance like the 2003 Charlotte airport crash: https://en.wikipedia.org/wiki/Air_Midwest_Flight_5481

    Yes, there was misloading, but maintenance was certainly an issue. As pilots, we can only do the best we can.

    In that instance, what do you do if the aircraft suddenly pitches up on the takeoff roll?
     
  24. David Megginson

    David Megginson Cleared for Takeoff

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    It's easier for a light piston, where you're not likely to end up in a fire if you go off the end of the runway. In my case, if the wheels have left the ground, push the nose down first, then (in either case) cut power and do my best to stop on the remaining runway. Or was that a trick question?
     
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  25. Divine Wind

    Divine Wind Pre-Flight

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    Yes, emergency stop. Screw the V1 crap; if the nose pitches up and full forward stick has no response, it's do or die. Idle throttle, full nose down, maximum braking.

    Better to live and explain it to the FAA than to risk killing all aboard.

    FAR 91.3 prevails over V1 or any manual....saying "declaring an emergency" as you are aborting or once under control is good. The FAA understands Aviate, Navigate, Communicate. Just slip the emergency declaration in there at some point.

    91.3 Responsibility and authority of the pilot in command.
    (a) The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft.

    (b) In an in-flight emergency requiring immediate action, the pilot in command may deviate from any rule of this part to the extent required to meet that emergency.

    (c) Each pilot in command who deviates from a rule under paragraph (b) of this section shall, upon the request of the Administrator, send a written report of that deviation to the Administrator.
     
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  26. BocaFlyer

    BocaFlyer Filing Flight Plan

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    Just an update on this... I took a tapered wing Cherokee for a flight last night and it took off very similarly to the Cessnas I trained in.

    I'm going to take a look and double check the trim settings the next time I fly the Hershey Bar winged airplane. Thanks for the great discussion!
     
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  27. Piper18O

    Piper18O Pre-takeoff checklist

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    Cherokees are generally nose heavy to the far front of the cg window, and often with 2 people up front and nothing in the back or baggage, they will by outside the cg window forward. While not ideal, cg forward is not nearly as dangerous as cg aft if a stall takes place because aft could result in a unrecoverable tail slide. I don't know it Piper designed it this way on purpose or it just happened to end up that way. Regardless, Cherokees are really not that hard to fly if you understand this fact and adjust accordingly. Takeoff in a Cherokee will almost always need the trim tab aft of neutral, especially with no weight in the back. When I take off in a Cherokee, if I notice as I rotate at the proper takeoff speed that it feels heavy, I just crank up the trim to lighten the feel a little. Your speeds are the most important and I trim accordingly. If I am going the right speed and the controls feel heavy, I adjust. It has become so automatic that I don't even think about the fact that I am adjusting the trim. I use the same method on landing as well. If the control feels heavy I trim aft, if it is light, I trim forward. It really doesn't take long at all to get used to trimming on the fly, and it only takes a second or two. Just remember that your speeds are very important. Trim the plane as needed for the feel of the yoke while going the proper speeds. If the plane is trimmed properly, it is likely to feel much more like the Cessna that you learned on than if it is out of trim, regardless of whether it is the hershey bar or tapered, however the tapered will be closer to what you are used to. I sometimes think I fly more using the trim wheel than the yoke, not just on takeoff and landing, but on climb and descent as well.
     
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