Hangar Flying => Hangar Flying => Topic started by: Bill James on June 14, 2011, 09:45:13 PM
Title: Thoughts on Operating Weight
Post by: Bill James on June 14, 2011, 09:45:13 PM
The note that I wrote on flight characteristics was pretty light and carefree. However, it wasn't done lightly. Ha. And that's the problem, weight matters :) There was some pretty significant prep on me and the plane beforehand. These include personal training, practice, the annual inspection and things like the BFR. FWIW, Here are a few thoughts. - My airplane’s minimum speed is higher at heavier weights. Sure. A no brainer, right? But how does that affect us? I observed this while doing slow flight with a pretty solid GIB (Guy in Back). The airplane just would not go slower that 80 indicated. Not having thought about it that day, I expected the minimum speed to be about 55 or 60 indicated, as on the recent test flight. However, that flight was made with me and 8 gallons. This flight, besides me probably not holding my tongue right, included over twice that fuel, warmer temps, and a solid young adult in back. To me there are two immediate issues in flying at higher gross weights. One, its hard on the landing gear attachment area. How many of us imagine compensating for higher operating weight by simply just always making feather soft landings? And then do it every time? Ha. Two, another bad thing, in a forced landing at higher weights the ground speed and inertia are higher. We are just more at risk to damage and injury and a more sporty arrival when we just can’t slow down to the aircraft’s optimum touchdown speed. Any airplane.
BTW, I didn’t do slow flight without preparation. It is not part of our normal flight operations. Rather, it must be done very carefully and deliberately with every airplane during the restricted period, after purchase, or after a mod like final paint, to confirm that when we are in normal flight, that if for some reason we do get unusually slow, that the plane will in fact operate as designed and protect us. Follow the POH and CPs in accomplishing that minimum speed test operation. You don't just go out there and go to full back stick the first time. Do the homework :)
I would not have done slow flight with the passenger if I hadn’t recently tested my plane and confirmed proper handling at full back stick. Because of time I chose not to demo aileron or rudder turns at minimum speed with him, although I had recently done them solo. Also, I backed him up on the sidestick so he wouldn’t do anything unexpected and force the plane out of controlled flight, and so I could make immediate inputs if needed. So those are a few of my thoughts on the plane insisting on a higher minimum speed than I desired.
A couple more general thoughts. A bush pilot had an angle of attack indicator on his wing strut, with best AOA marked in red. Using that he could always climb out, or approach, at the best angle, which was always the same AOA, regardless of weight. But the speed varied greatly. He also noted that the airplane always stalled at the same AOA, but the stall speed varied greatly between high and low weights. Same for us. Our approach AOA can be the same, but higher weights will always have higher speeds at that particular angle, no matter whether we hold our tongue right or not. And for us, our speed at max lift/min speed may be much higher than we expect or want. And remember, in an emergency landing, to arrest the rate of descent, we need to maintain at least 22 mph over that minimum speed until flaring.
As with any airplane, use extreme caution when doing things that you haven’t done in awhile. An example was a new private pilot in a C-172 with his girlfriend that somehow ended up doing multiple circles at 60 degrees bank at 400 feet over his parent’s house. - Not something the instructor had done with him a lot in training.
Another thought, here on a hot day the air on the 700 foot msl runway may be at over 4000 feet density altitude. It is prudent to follow the mountain flying practice on takeoff before releasing brakes of going to full throttle and then lean to peak.
Another? - Operating an airplane at gross or over-gross weights will probably result in at least minor damage to the landing gear attachments.
Another?… Concerning building a light aircraft. I have heard and felt others say, and have caught myself thinking, “My airplane will be the lightest one ever built, and the fastest, because… because… I really care. Ha.
I know we all know this stuff. Thanks for coming along anyway.
Oh yes, one more thing. You do remember the one "constant" that they maintained on the Voyager all nine days, right?
Title: Re: Thoughts on Operating Weight
Post by: ekusafetyman on June 16, 2011, 01:25:43 PM
Great post! Thanks for the reminders and thanks for the original post! :)
Title: Re: Thoughts on Operating Weight
Post by: dorr on June 20, 2011, 02:09:37 PM
Interesting weight topic..
Oddly enough, or perhaps because of wing loading, the Varieze seems to take much more notice of weight than the Long EZ, or my Berkut. However, I took my little boy, 320 lbs, to Catalina last week and bounced it on because of the extra weight, we fell the last 2 feet. He's an aero engineer and said, on final, 'gear down, and add power for my extra weight."... I also thought - nobody lands hot at Catalina - my mistake....
I used to win landing contests at the R.A.C.E. events by pounding it on - had the gear start slopping fore and aft (inches at the axle end) after a few years of harder than normal landings; it was gear that Mike Melvill and Dick Rutan worried about when 1000 lbs over gross on their southern ocean flights; only had one really heavy landing though...