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3 Answers

VLE and VLO speeds…which is higher and please define

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Private Pilot

I would like to know about Vle and Vlo and which airspeed is generally higher?  ALso the definitions would be good to have as well!  Thank you CFI!

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3 Answers



  1. Steve Pomroy on Feb 10, 2011

    Hi Kyle.
     
    Both Vle and Vlo pertain to landing gear limitations.  Vle is the maximum speed at which the landing gear may be Extended, and Vlo is the maximum speed at which the landing gear may be Operated.  “Operated” in this context means transitioned from up to down or vice versa.  “Extended” in this context mean down and locked.  Some confusion is sometimes caused by the double meaning of the word “extended”, where “gear extended” generally means down and locked, but “extending the gear” means transitioning the gear from up to down.
     
    In some aircraft, Vle and Vlo are the same.  But when they are different, Vle will be higher.  The gear operation may be limited by things like hydraulic system pressure limits, air loads on gear doors that retract after transition, or air loads on the joints and linkages that are out of place during transition but in place and strong when the gear is down and locked.  In some aircraft, these limitations are not limiting, and the gear can be operated all they way up to the maximum extended speed.  In some other aircraft, the gear must be operated at a reduced airspeed, but once the gear is down and locked, the airspeed can be increased.
     
    It’s also possible to have multiple Vlo’s.  The Piper Seminole has a Vlo for extending the gear, and a different Vlo for retracting the gear.  I don’t recall the numbers right now, as it’s been a long time since I’ve flown the Seminole.  But if I recall correctly, one of the Vlo’s in this case is also equal to the Vle, the other is lower.  I also seem to recall that the reduced Vlo in this case is due to a limitation on the hydraulic system, but don’t quote me on that:).
     
    Cheers,
    Steve
    http://www.flightwriter.com

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  2. MaggotCFII on Feb 11, 2011

    Adding this from FAA 8083-25A  “Pilot’s Handbook of Aeronautical Knowledge”, Ch 10, Performance Speeds, pg 10-17:
    “Vle – the maximum speed at which the aircraft can be safely flown with the landing gear extended.  This is a problem involving stability and controllability.”
    “Vlo – the maximum speed at which the landing gear can be safely extended or retracted.  This is a problem involving air loads imposed on the operating mechansim during extension or retraction of the gear.”
    If you don’t have a “hard copy” of the handbook, it is available for download at the FAA site.
    Enjoy!

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  3. Brian Campbell on Feb 11, 2011

    VLo Up – 200
    Vlo Down -250
    VLE – 250
    So this says you can put the gear down at 250 – and fly with it down and 250 but to retract it you must be less than 200.  The different speeds are generally a result of aerodynamic forces acting on the gear in transition.  
    If the gear retracts towards the nose it goes against the wind therefore the hydraulics have to work much harder to 250 than they do at 200.  On the other hand when you put the gear down the wind is assisting the extension of the nose gear.

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