COZY MKIV V-n Diagram

Normal Category, 2050 lb., Sea Level


This image shows the V-n diagram for the Max Gross Weight case for a COZY MKIV in the Normal Category at Sea Level.

The curved black lines on the left are the extent of the maximum G's that can be applied by full elevator travel (assuming that it's possible to stall the aircraft either positive or negative) and the horizontal and vertical red lines are the extent of the Limit Load (3.8 g).  This is the load for which the aircraft was designed (for Normal category aircraft).  The outer black lines, horizontal and vertical, are the extent of the Ultimate Load (1.5 * Limit Load).  This includes the proscribed safety factor that the FAR's require.  Of course, since the COZY is not certificated and no structural testing has ever been done on it, we have no clue how accurate these limits may or may not be.

In this case, Va (maneuvering speed) is 138 mph IAS, with a Vs (stall speed) of 71 mph (Va is alway Vs * sqrt[max positive load factor] ).  Vb (the gust limit) is 141 mph, and is shown here as the minimum speed at which either a positive or negative 50 fps gust will create the maximum load factor in the appropriate direction.  We can see that Vb is higher than Va in this case.  Vc_min is the lowest allowable defined cruise speed (per the FAR's), and would be 148 mph for the COZY in this condition.  It can be higher that that, but not lower. Vd (dive speed) is Vne/0.9, and is the speed that the aircraft theoretically should be tested to in the Phase I period.

We can see that in VERY rough air, we should slow down to less than 141 mph, and if we're planning on full positive elevator deflections, to below 138 mph. In merely rough air - 25 fps gusts - we can fly all the way up to Vne without structural problems.

I must admit that I'm not confident in my interpretations of Vb and Vc - if anyone has input on their true meanings, per the appropriate FAR's, I'm all ears.


[Normal/2050/SL] [Normal/2050/12.5] [Normal/1500/SL] [Normal/1500/12.5] [Utility/2050/SL]

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Copyright 1995 - 2016, All Rights Reserved, Marc J. Zeitlin
e-mail: marc_zeitlin@alum.mit.edu

Last updated: April 11, 2016