Utility category gross weight?

[rightrudder]

My understanding is that a Utility category gross weight is for the purposes of loading when doing any sort of aerobatics. So, with the non-aerobatic -9, why is the Utility gross weight even listed in the plans?

[terrye]

Nope. There are three categories of certification (for certified aircraft).
Normal +3.8G/-1.52G
Utility +4.4G/-1.76G
Aerobatic +6.0G/-3.0G

Each category allows for certain flight maneuvers.

[grubbat]

My guess is to give us an idea of how much we can increase the g margin thru weight reduction.

What would be cool is to be able customize our build to increase a G here or there besides weight reduction or speed reduction. I'm not talking about a third party offering, but real sound engineering designs for the -7 person who may want to take, say a 3G tail up to a 4G, or the -8 person who wants to add 1G to the wing or whatever.

Originally Posted by rightrudder

My understanding is that a Utility category gross weight is for the purposes of loading when doing any sort of aerobatics. So, with the non-aerobatic -9, why is the Utility gross weight even listed in the plans?

[tjo]

As terrye says, thee are 3 categories. Utility and aerobatic are for aerobatic, but any aerobatic manoevers, they need to be demonstrated during flight testing.

For what it is worth Citabrias are utility category, but are respected aerobatic airplanes...

Tim

[rightrudder]

Thanks, guys. A Utility category gross weight of 1600 lb. is listed for the -9A, so it's good to know that solo with full fuel I'll be under that weight. You never know when you're going to pull 4+ g's through, say, an inadvertent Lomcevak when passing through wake turbulence.

[terrye]

Well it doesn't say anything about lomcevaks, but here is the text from FAR 23.3

23.3 Airplane categories.

(a) The normal category is limited to airplanes that have a seating configuration, excluding pilot seats, of nine or less, a maximum certificated takeoff weight of 12,500 pounds or less, and intended for nonacrobatic operation. Nonacrobatic operation includes:

(1) Any maneuver incident to normal flying;

(2) Stalls (except whip stalls); and

(3) Lazy eights, chandelles, and steep turns, in which the angle of bank is not more than 60 degrees.

(b) The utility category is limited to airplanes that have a seating configuration, excluding pilot seats, of nine or less, a maximum certificated takeoff weight of 12,500 pounds or less, and intended for limited acrobatic operation. Airplanes certificated in the utility category may be used in any of the operations covered under paragraph (a) of this section and in limited acrobatic operations. Limited acrobatic operation includes:

(1) Spins (if approved for the particular type of airplane); and

(2) Lazy eights, chandelles, and steep turns, or similar maneuvers, in which the angle of bank is more than 60 degrees but not more than 90 degrees.

(c) The acrobatic category is limited to airplanes that have a seating configuration, excluding pilot seats, of nine or less, a maximum certificated takeoff weight of 12,500 pounds or less, and intended for use without restrictions, other than those shown to be necessary as a result of required flight tests.

(d) The commuter category is limited to multiengine airplanes that have a seating configuration, excluding pilot seats, of 19 or less, and a maximum certificated takeoff weight of 19,000 pounds or less. The commuter category operation is limited to any maneuver incident to normal flying, stalls (except whip stalls), and steep turns, in which the angle of bank is not more than 60 degrees.

(e) Except for commuter category, airplanes may be type certificated in more than one category if the requirements of each requested category are met.

[rightrudder]

Terry, what you've posted is mostly clear in my mind. The question is why the RV-9A plans list a Utility Class Gross Weight of 1600 lb. Does this mean it's approved for limited acrobatic operation (for example, an 80-degree steep turn) as long as the Gross Weight is 1600 lb. or less?

Sorry if the question seems obvious; I'm just seeking absolute clarity here.

[terrye]

In the RV-9A instruction manual Van's recommends against spins saying on page 15-19 "The RV9/9A is not intended for spins at all". In addition they say "Van's Aircraft Inc. does not consider spins to be a recreational aerobatic maneuver, and recommends that they not be casually undertaken". So you can take spins off the list of maneuvers, even in the utility category. That leaves lazy eights, chandelles and steep turns. However, it's up to the builder/test pilot to check these in phase 1 testing.

In my view (and keep in mind I'm not the designer of the airplane) the reason for having a "utility weight" is not so much to approve it for the above maneuvers, as to build in some extra strength for normal flying. In particular, the RV9/9A has a fairly low maneuvering speed compared to it's cruising speed, so unexpected turbulence might exceed the 3.8 G limit if it was designed in the normal category. Taken another way, if you are at the 1750 lb gross weight and know you are flying in turbulent air, it would be wise to slow down to maneuvering speed.

I don't fly aerobatics (which is why I chose the RV-9A), and while it's possible for someone like Bob Hoover who can fly loops and rolls in a twin like the Rockwell Commander to do the same in an RV-9A, for the inexperienced pilot it's easy to exceed the limit loads (that is break the airplane) if something goes wrong in a recovery from a botched maneuver.

Aerobatics are for aircraft like the RV-3, 4, 6, 7 and 8 that are stressed to +6/-3 G.

[rightrudder]

Good explanation. I plan on treating it as a Normal Category aircraft in all load scenarios, so the extra g tolerance when lightly loaded is a bonus/safety factor.

[Mel]

Originally Posted by terrye

Aerobatics are for aircraft like the RV-3, 4, 6, 7 and 8 that are stressed to +6/-3 G.

Just remember that these load limits are NOT at normal gross weight.
There is a separate (lower) gross weight limit for aerobatics.