Welcome Guest. Sign in or Signup

4 Answers

Maneuvering Speed

Asked by: 2439 views Aerodynamics

You want to be at or below Va when performing steep turns, chandelles, lazy eights. I know that Va decreases with a decrease in weight and Va increases with a increase weight. I also understand the logic applied to using Va when flying straight and level during turbulent conditions and the relation of AOA to weight. I do not completely understand Va as it relates to performing maneuvers.

Question: Pertaining to maneuvering (steep turns, chandelles, lazy eights) why does Va decrease with a decrease in weight and Va increase with a increase weight? 

 

Thank you for the feedback.

Ace Any FAA Written Test!
Actual FAA Questions / Free Lifetime Updates
The best explanations in the business
Fast, efficient study.
Pass Your Checkride With Confidence!
FAA Practical Test prep that reflects actual checkrides.
Any checkride: Airplane, Helicopter, Glider, etc.
Written and maintained by actual pilot examiners and master CFIs.
The World's Most Trusted eLogbook
Be Organized, Current, Professional, and Safe.
Highly customizable - for student pilots through pros.
Free Transition Service for users of other eLogs.
Our sincere thanks to pilots such as yourself who support AskACFI while helping themselves by using the awesome PC, Mac, iPhone/iPad, and Android aviation apps of our sponsors.

4 Answers

  1. Best Answer


    John D Collins on Mar 11, 2014

    Dan, you will sometimes get two answers regarding Va. Some will say it is a fixed reference speed defined in the certification process and is established at maximum gross weight. Others will say it varies with weight by the square root of the ratio of the weights. The actual g load that the wings carry at the stall varies with weight at Va, but the load measured in pounds of lift does not. This means that the wings will stay on a lighter weights than Va, but the wings are not the only structures affected by the g forces and it is these structures that may break.

    At Va adjusted for weight, the airplane will stall and will not exceed its certified design load factor. As you increase the g load to Va, the g load reaches a maximum at the point of the stall. A very important point, Va is only specified in the pitch axis direction and if there are simultaneous loads from ailerons or rudder, there is no guarantee that something might not break, for example the American Airlines Flight 587 crash in 2001.

    +3 Votes Thumb up 3 Votes Thumb down 0 Votes



  2. Mark Kolber on Mar 11, 2014

    Dan, I’m not sure I understand your question.

    Why would you think the explanation would be different for maneuvers (where you are adding load to the aircraft) than for straight and level flight in turbulence (where something else is adding load to the aircraft)? Va (as John said, established for max gross) decreases with weight in a maneuver for exactly the same reason as in straight and level flight.

    +1 Votes Thumb up 1 Votes Thumb down 0 Votes



  3. Dan Chitty on Mar 11, 2014

    John,

    Great points you made. Much appreciated.

    Mark,

    Thank you for the response as well.
    But, based upon your feedback and John’s feedback I see that Va theory for straight and level flight in turbulence also applies to maneuvering flight. Since maneuvers produce a increase in wing loading, the same staight and level turbulent Va theory applies to turning maneuvers.

    0 Votes Thumb up 0 Votes Thumb down 0 Votes



  4. Brian on Mar 16, 2014

    There is no reason you cannot do a steep turn, chandelle, and especially lazy 8’s at a speed above maneuvering speed. Maneuvering speed protect the pilot from damaging the aircraft if he or she over controls the aircraft. A loop is typically entered close to, if not in, the yellow arc. Clearly well beyond maneuvering speed.

    I make a point to mention this because years back I flew a photo flight with a gentlemen who was himself an instructor. We were in a 172RG over the NY class bravo for the purpose of traffic survey and flying at a speed just shy of Vno. At one point I made a 60 degree bank turn and was met with an interesting argument. His claim was that I could over stress the airplane if I did steep turns above Va.

    It’s a fundamental misunderstanding of what maneuvering speed is and how load in a turn works. A 60 degree bank turn at 50 knots or Mach 7 is a 2g turn. Speed is not a factor. If your aircraft can handle 3.8 (normal) or 4.4 (utility) g’s than a 60 degree bank at any speed will not over stress the aircraft. It will impart 2g’s period. The private pilot steep turn experiences a mere 1.4g load. Lazy 8’s and chandelles barely go over 1g.

    The point of maneuvering speed is to be aware that above that speed making sharp or full control inputs can result in failure of the airframe. As long as your inputs are smooth and deliberate you can safely perform most maneuvers, including many aerobatic ones, above Va.

    As John points out it is important to keep three things in mind when thinking about this speed. Va provides protection if the stall is progressive, symmetrical and the structure is in pristine condition. Snap stalls, asymmetrical stalls (like that Airbus crash), and weaker aged structures may still result in airframe failure.

    OP, do you know how stall speed vary’s with weight? If so Va is a function of Sqrt(load factor) times stall speed.

    -1 Votes Thumb up 0 Votes Thumb down 1 Votes


Answer Question

Our sincere thanks to all who contribute constructively to this forum in answering flight training questions. If you are a flight instructor or represent a flight school / FBO offering flight instruction, you are welcome to include links to your site and related contact information as it pertains to offering local flight instruction in a specific geographic area. Additionally, direct links to FAA and related official government sources of information are welcome. However we thank you for your understanding that links to other sites or text that may be construed as explicit or implicit advertising of other business, sites, or goods/services are not permitted even if such links nominally are relevant to the question asked.