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Flying overgross with CG slightly beyond aft limit

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Aerodynamics

Here is the scenario.  I will be flying my Piper Seneca II around the world (refer to:  http://www.WingsAroundTheWorld.INFO) and will be installing ferry tanks and getting the necessary FAA approvals for operating at 25% to 28% over gross weight.   Because I will be a 'test pilot' on this mission, I fully understand the implications of being over gross weight.  The aft limit for the CG in the PA-34 is 94.6 (regardless of the weight).   Forward limit is 82.   The current design of the ferry tanks indicates that the CG may end up at 96 or 98 - and that is with 150 pounds of fuel in the nose.  Is there a legal way that I can emulate or simulate actually flying with the CG at 98?  I understand about the control issue and recovery from turbulence.  However, the FAA waiver will stipulate 'no turbulence', so the goal is wait when necessary to have smooth air (at least for the first 3-4 hours of the 14 to 16 hour legs).  What advice can you offer? 

Thank you!  Also, let me know if you are interesting in being a co-pilot on the mission!

 

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3 Answers



  1. John D Collins on Oct 16, 2014

    My advice is to find a way to keep the CG within the limits. I would not be willing to fly in the aircraft with it being aft of the rear CG limit. Over gross is one thing, controllablity is another. If you lost an engine, your VMC would be higher, but unknown. Put ballast somewhere forward to move the CG forward. If you are taking another pilot on the mission after your test, use ballast to simulate his weight. I would rather be a little heavier if necessary.

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  2. Gary on Oct 18, 2014

    Tim, flying outside the envelope is not something you want to do. As you know, aircraft performance number’s are based on staying within the envelope. You mentioned the FAA waiver will stipulate ‘no turbulence.’ Can you depend on having no turbulence when flying that distance. Better re-think the W&B.

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  3. Tim Fino on Oct 18, 2014

    Gary:

    I appreciate the concern of flying outside the envelope. I routinely offload fuel when I have 3 or 4 passengers to stay in the envelope, However, this is a different situation and is frequently done, with the FAA’s approval. The aircraft will fly with the extra weight – that is not the issue. The issue is the CG.

    We have re-worked the numbers and found a way to keep the CG at the aft limit (by making a 37 pound lead weight attached to the inside nose of the aircraft, at the datum line). With the extra 37 gallons of fuel AND the weight, the CG is moved to exactly the aft limit. That means I will be flying at 28% to 29% over gross – but the FAA approval will be for 30% over gross so it should be ok.

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