CS Prop and Performance Profile settings?

I need some assistance in obtaining my performance profile for the RV-10.

When figuring out Vy, Do I leave the CS prop full forward throughout all testing speeds? (say 120 knots down to 85 knots).

What about all the other profile speeds (cruise climb, climb, descent, approach, non-precision approach etc.) What are the ideal settings for the prop to be set at? 2400 RPM? Then the only things that I would have to dial in are the pitch and MP.

I've seen other peoples numbers but would like to know how to best utilize the CS prop in establishing the numbers.

john

What makes Vy the best rate of climb? Excess power. How does your engine make the most power? Full throttle and maximum RPM.

There's no ideal as such, just pick the common numbers that have been used since the beginning of time, note the results then fly happily ever after
One variable to consider is the performance achieved above S/L assuming you have a normally aspirated power plant -

No ideal?

Really? I always wondered where the performance numbers came from...I guess you just pick them...

A few thoughts:
* Join EAA to get access to additional support. VAF and EAA each have advantages;
* EAA has just come out with a guide to flight testing, including test cards and a full test program. It's voluminous because there's lots of relevant material. I'm not sure if the rule has been implemented yet, but if you use their guide, you may not need to fly a full 25 or 40 hours. Well worth the cost;
* Get full operating limitations and guidelines from the folks who custom built your engine;
* EAA has a Flight Advisor program (I'm one) to help folks plan their flight test program. A good Flight Advisor can help you a lot;
* EAA also has a program where an *appropriately* experienced pilot can fly with you on the first and subsequent flights. The experience and recency requirements are steep, including time in the same make and model. For example, I meet the requirements for RV-9A but no other;

Getting into more nitty-gritty:
* Vy is determined in flight test. There are references to doing that, but if your avionics have data recording, you can probably do the job faster and easier, although I've not seen a reference;
* In climb, the factors you trade off are engine power, cooling, fuel flow, airspeed (for getting somewhere), cabin noise, outside noise, and view over the nose. Carbureted engines typically run extra rich at full power for extra cooling. With your cowling, you may need to climb faster than Vy for cooling. (Even the lowly Cessna 150 at one point recommended climbing above Vy for engine cooling). And being a good neighbor (prop noise) may mean a power reduction right after takeoff;
* One of the tradeoffs in light airplanes flown in the ATC system is speed variability. Sometimes you slow down for traffic, sometimes you speed up. Yesterday, for the first time in my flying career, ATC asked me for minimum speed and maximum speed on the same approach! A significant goal on approach / pattern is to always have the airplane in trim, and if you deliberately fly with changing speeds (sometimes you have to), make sure that you have the airplane in trim long enough before the flare to be comfortable. The same criteria that you use in other airplanes (start with the book values, modify as appropriate for the situation you're in) apply to the RV-10.

One of the key points that Rutan advised in the days of the VariEze, when transition training was not available, was to get really good in two dissimilar aircraft before you did your first flight. That's still good advice, even if you get type-specific transition training, and that is available for the RV-10. (I could not find it for the RV-9A and wanted it, even though I had 3000+ hours, ATP/CFII).

I'll be at Sun n Fun and we can chat, or if you prefer, PM me your phone number.

Ed Wischmeyer
EAA Flight Advisor

Vx and Vy are reference speeds created to help guide the pilot in achieving max performance or efficiency. In my opinion, Vx adn Vy should be provided for the normal climb configuration recommended in your POH or typically used by you. Most certified aircraft provide a recommend RPM for climb after initial 500-1000'. I would expect Vy to be provided in that climb configuration.

I would expect most take off at full fine and Vx is most used for obstacle clearance during take off, so test in that configuration. I would also expect most folks pull back to 2500 for sustained climbs and would measure Vy there. However, modern testing protocol calculates both from the same test, so will need to pick one or the other or run the test at both.

Larry

rdrcrmatt said:

What makes Vy the best rate of climb? Excess power. How does your engine make the most power? Full throttle and maximum RPM.

Click to expand...

let me offer a different thought.

Vy is an efficiency number and not a max performance number. Vy provides the angle of attack or air speed the produces the greatest rate of climb relative to distance travelled (it presumes you want the highest cimb rate available at the most efficient mix of vertical and horizontal distance travelled) for a given power input, typically the recommended climb power configuration. Vx is a max performance number that provides the angle of attack or airspeed that provides the greatest rate of climb, isolated from other criteria (factors only max vertical speed attained).

Vx it typically needed when the pilot wants to get high quickly and therefore max power is fair to assume. Vy is needed when the pilot is in a sustained climb and desires maximum vertical component, without unnecessarily degrading forward speed, as is the case at Vx speeds. It is most used in a typical climb setting and not a full power setting. Unless, of course, the pilot climbs at full power which I would expect to be atypical at RV-10 FF rates.

Guys,

This somehow got out of hand. I went flying this morning and calculated my speeds. My Vy is 100 knots.

What I was looking for was settings for the PROP to give me an idea of what settings I should look for in my plane. Here's what I got.

Examples I got this morning:
Straight and level at 120 knots
MP 23.7 ", RPM 2410 Pitch -2.5 Speed 120 knots

500 fmp descent
MP 18.1", RPM 2410, Pitch -2 Speed 120 knots

20 degrees Flaps
MP 23.7, RPM 2410, Pitch -3.5, 500 fpm descent at 120 knots

Landing config:
MP 11.1, RPM 2000, Pitch -6, Flaps 20, Speed 74 knots

Sorry for the wasted bandwidth.

john

Vx/Vy

lr172 said:

let me offer a different thought.

Vy is an efficiency number and not a max performance number. Vy provides the angle of attack or air speed the produces the greatest rate of climb relative to distance travelled (it presumes you want the highest cimb rate available at the most efficient mix of vertical and horizontal distance travelled) for a given power input, typically the recommended climb power configuration. Vx is a max performance number that provides the angle of attack or airspeed that provides the greatest rate of climb, isolated from other criteria (factors only max vertical speed attained).

Vx it typically needed when the pilot wants to get high quickly and therefore max power is fair to assume. Vy is needed when the pilot is in a sustained climb and desires maximum vertical component, without unnecessarily degrading forward speed, as is the case at Vx speeds. It is most used in a typical climb setting and not a full power setting. Unless, of course, the pilot climbs at full power which I would expect to be atypical at RV-10 FF rates.

Click to expand...

I think you have Vx and Vy mixed up. Vx is best angle of climb and Vy is best rate of climb. They both need to be determined at max power (full throttle and full RPM).

Skylor

skylor said:

I think you have Vx and Vy mixed up. Vx is best angle of climb and Vy is best rate of climb. They both need to be determined at max power (full throttle and full RPM).

Skylor

Click to expand...

Yes, it's been too long since I did this. Vx is the speed for max vertical distance in the shortest horizontal distance and Vy is max climb rate. While you may be correct that it is normally measured at full power, most pilot should also know their Vy at normal climb power settings, as they may be different. On my 6 with an FP, I had two different Vy speeds that resulted in the same climb rate (both with the same power level) with a fall off between them.

Larry