optimum altitude

G

gzlf3p

New member
All of you who fly the Bellancas on cross-country trips no doubt have an optimum altitude. Maybe some of you have a window where speeds slowly increase and then decrease. There may even be a flat spot if we could graph these results. My Cruisemaster seems to get weak on power and a little slow around 12 thousand feet. I was indicating 135 MPH (give or take) but seemed to need a lot of nose up to maintain altitude.

GPS would make all of this very ease.
 
If you look at the "cruise and range" charts in the owners manual (the older models do not have this) you will see that the airplane performs best at about 8500 feet. I have the original manuals for the 14-13's, the 14-19, 14-19-2 and 14-19-3. The engine power really doesn't make much difference in the alt/power ratio, as they are ALL normally aspirated engines and loose HP at the same rate as the air thins. The "sweet" altitude, without turbo, is a result of the trade off between better performance at higher altitudes due to less air resistance for the same lift and the loss of power on normally aspirated engines due to the thinner air (density altitude). I hope this helps.
 
This is no plug for the Club's archives, but if you buy the older newsletters from an earlier incarnation of a Bellanca Club, there is a test performed by one of the -2 guys. He got his to 19K, and checked performance at that altitude and below. Yes he had oxygen fed through a mask. Yes, it was legal back then to fly above 18k without ATC guidance.

Power does make a difference. Although the sweet spot mentioned is accurate, performance higher than that is simply a reduction of the percentage of rated horsepower. A light 'Master with 230hp still makes slightly over 170hp at 8000 feet, running 50 degrees rich of peak. A mid-time O435 is lucky to make 170hp at sea level. As we all know from our basic flight training, climb is a product of thrust exceeding the power needed to maintain level flight.

Much depends on the wing, of course. I recall a narrative written by Luscombe's Chief Engineer of a night flight to Newark in the late '40s. He found the glass layer at 15k, relaxed (you could not lean back with those bench seats), turned in a radio station on his ADF, and lit up a cigarette as he enjoyed the ride. The only other traffic as he approached Newark was a single Convair. The engine on the airplane was a C90, but every ten square feet of wing was charged with hoisting one pound to aloft.

Many factors influence service ceiling. How high I fly depends on winds aloft. I carry oxygen. Higher often means stronger winds. If I can catch a 30kt tailwind at 12.5, I'll go a lot faster than if I have no tailwind at 8,5.

Then again, the only time I actually had to use my oxygen tank was when I was flying from Seattle to Austin, and there were fires around LA - they seem to be a feature of the area nowadays. The oxygen allowed me to ignore the choking smoke.

In short there are no hard rules here. If you're wallowing at 12.5, though, that's an inefficient way to fly. Robbie Back did not baby that engine. When I flew with him, for example, around Blakesburg, he'd use to prop control as an air brake to slip into formation with buddies. He said the engine was tired anyway and he planned to rebuild it that winter. He thought harder about it later, realized he only needed two seats at that time in his life, and sold the Bellanca.

I hate to say it, Jerry, but I'd run a compression check on your bird.

Jonathan
 
Tim,
Would you be willing to share the performance charts for the Cruisair? I just love that kind of stuff. I have been hacking away at trying to put something together, but not overly successful. Neither my Franklin or Bellanca manuals have any kind of charts. Larry
 
Ah, Red :) :) :)

Yeah, I got a mite too involved in the subject there :oops:

I've logged a lot of cross country flights in a slow airplane. Hence my interest in such things.

Jonathan
 
Picking up on what Pete posed in the Phoenix A&P topic, quote:

"There is a great book out there called "Flying the Beech Bonanza" by John Eckalbar that calculates all the fine points of efficient flying. Though applicable to the Beech, the principles of the book can be extrapolated to any plane. In one chapter, he calculates climb speed, cruise speed, and descent speed (and fuel flows) and demonstrates that for different mission lengths, different altitudes are appropriate. It turns out that it takes an amazingly long trip to justify the long climb to altitiude. I have long since lost the book, but as I recall it was 150 miles before it was worth climbing over 2000 feet and to climb to 8000 was at about the range of most of our planes. I like the quiet of high altitude, so I usually ignore the advice, but if keeping the trip short is important, don't climb. (Then again with my home field having an elevation of 5900 feet, cruising at 2000 is rather tough."
_________________
"Peter S (petersch@exwire.com"

Sounds a bit like one of those scentifically provable but wholly impractical pieces of wisdom. 2k is one bumpy altitude is most places a lot of the time. I'd take Red's 5k over that :)

Jonathan
 
2000 may not work for many of us but when chosing between 6500, 8500, or 11,500, it turns out to be faster and cheaper to stay low unless travelling greater than about 500 or 600 miles.
 
We're talking zero wind here. I just made two flight of a little over 100 miles (Creswell to PDX) and on both flights I had tailwinds in BOTH (!!!) directions. One round trip per day, two hours apart, but each round trip was on a separate day. Went north at 6.5, south @ ~ 2.5. Now this isn't something that ever happens to me very often, but it sure shows it's worth checking the winds for even relatively short flights. The flight times on these flights was shorter than flights I have made when the winds were calm. I climb at 95-105 mph IAS. I indicate ~120 mph in level flight. Descent into Portland kind of depends on ATC, since I ususally have to cross midfield 2000 AGL and make a Stuka approach. My pitot static system is very accurate, so when I calculate TAS, it is pretty good, as previously verified by GPS runs. (Some of you may have seen my plane with the gigantic pitot tube sticking out on the left wind...first time I saw the plane, I thought he had a 20 mm cannon sticking out of it...never saw a counter-insurgency Cruisair before!?)
 
Actually, I have more fun when I fly where I can still see the ground ( yet still miss the mountains), set the fuel burn at some acceptable rate , the motor purrs ( which Continentals do) , the air is smooth, cover up the airspeed , stop looking at the GPS, and use only my watch. I like flying. No I LOVE flying, and one day on my way from Spokane to Livermore I asked myself why, since I supposedly love to fly, am I always trying to get there faster?
 
That was a paradox that surprised me when I lived in Texas, Red. My best flying buddy and I both had Luscombes. Although not as lightly wing-loaded as, say, a T-Cart, you really feel the bumps. But every Texan I flew with preferred to fly low whereas my chief determining factor was not speed or efficiency - it was climbing above those bumpy layers at 4k and below.

Ship to ship comms went something like this.

"Hey, now THAT was a good bump."

"That one knocked my feet off the rudder pedals!"

It had the flavor of turbulence one-upmanship.

You need to fly low for two reasons in Texas: the sense of speed in a VAST state, and the need to find landmarks in a SPARSE state. "Head east when you come to the McDonald's sign," was not a joke.

Let's face it, a GPS makes flying easier but flying by visual landmark identification is much - much - more fun. Besides, our triple tails handle turbulence with grace compared to aircraft from the humble to the mighty.

Jonathan
 
Actually that Russian setup with Johnson style rudder bars, foot straps, and single brake lever mean I fly something like a CJ/Yak trike without mods. Hmmmm....and the setup was designed to train future MiG pilots....nahhhh :)

You said Russian airplanes - plural. How many aircraft do you have, Red?

Jonathan
 
There was a AN2 at Reclaw flyin in east Texas a couple of weeks ago. He did a high speed pass ( looked about 120mph and a slow speed pass (looked about 30mph)

Have not been around much to comment. Lori and I went to New Mexico,Wyoming, Colorado, then Texas a couple of weeks ago in the Viking an then left for Cozamell for a week.( comercial flight) Cozemell has a very short runway. The 737 landed on the #'s applied full brakes and thrusters and still did not get stopped untill we passed the #'s on the other end. When we left the nosewheel left the runway when we past the turn around at the other end. :lol: :lol: :lol:
 
A buddy of mine from out your way, Randy, said that Reklaw had over 400 aircraft show up...something about the weather being good for a change. It was rained out the year I lived in Austin *and* had my Luscombe at Kittie Hill. I always seem to miss out on those BIG fly-ins that don't have the EAA attached to them :cry:

Jonathan
 
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