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I Don't Get It - FP vs CS

Prop

C/S use is not a big deal. Look at all the extra knobs and switches people add to their airplanes with the EFIS systems they install.
 
C/S or F/P

Flyguytki said:
Again personal preference, I would rather have a manual transmission over automatic any day. But that right theres proves the point. It all what you want, if you want simple, you cant get much more simple than one lever for power, push forward go fast pull back slow down.

-david
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Manual verses automatic isn't an accurate comparison. A far more accurate comparison would be a high tech constant velocity, infinitely adjustable automatic transmission verses a manual trans that is stuck in one gear for life. Allan :rolleyes:
 
I've heard this ONE too many times!

PerfTech said:
Manual verses automatic isn't an accurate comparison. A far more accurate comparison would be a high tech constant velocity, infinitely adjustable automatic transmission verses a manual trans that is stuck in one gear for life. Allan :rolleyes:
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Comparing a fixed pitch prop to a manual transmission stuck in one gear is also not an accurate comparison.
If that were "apples-to-apples", there would be many cars running around with a "one-gear" transmission. Only place I've seen this is on the drag-strip.
There are MANY airplanes flying just fine with F/P props.
When is the last time you saw a car on the road with a one-gear transmission?
 
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Does this count?

Mel said:
When is the last time you saw a car on the road with a one-gear transmission?
Click to expand...

It has a fixed pitch prop.

AEROCAR3.jpg
 
aerocar

Yes it does. And it's neither a good car or a good airplane.
 
DO YOUR RESEARCH GUYS!

This car did NOT drive on the road with a single speed transmission!
 
No, but it drove on the road with a fixed-pitch prop. I thought these were one in the same.

It had a 3-speed on the floor for driving the wheels. That's just like having a constant speed prop. ;)
 
Car Transmission analogy.

Mel is correct. The car trans analogy is flawed in showing a comparison between a F/P vs. C/S.

Fixed pitch: $ lower entry price; low maintenance; no mechanical rebuild needed; lighter weight; no loss in top speed.

Constant speed prop does have the advantage of helping to move the CG forward for a more usable useful load, depending on mission. Also C/S has the advantages of a climb prop at slower airspeeds, therefore allowing shorter takeoffs and climb capability.
 
Air is a Compressible Fluid

You guys are off in Never-Never Land.

There's LOTS of difference between turning a propeller (either CS or FP) in a compressible fluid and driving a tire on a paved road.
(Different way of saying that Mel is right again.)

Reminds me of a debate by a buddy who challenged a so-called expert on model airplane propellers after the "s-c e" wrote an article in the AMA (Academy of Model Aeronautics) magazine.

Put your thinking caps on. :)
 
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Where I work, we're building a car with a single gear fixed transmission and no clutch.

The trick is to use an electric motor that produces 100% torque at 0 RPM:D:D
 
I was just...

.... poking you guys... :D
(with my comment automatic vs manual transmission)

As already mentioned, I bet this post is just to poke us... ;)
 
HP=TxR

Since HP=Torque X RPM, I like to think of the blue and black knobs as 2 ways to add or subtract power, together or individually...

Darn handy and works every time it's tried...
 
Constant speed prop just gives you some extra versatility. Depends on the operator if that is worth the cost. To each their own.
 
It's really simple.

Do you want great performance at a lower cost, or do you want maximum performance and are willing to pay the difference. Excellent results either way.
 
Stupid question

What setting will slow down an airplane with CD, blue knob all the way forward or all the way back?
 
Moura said:
What setting will slow down an airplane with CD, blue knob all the way forward or all the way back?
Click to expand...

Blue knob forward results in fine pitch and maximum drag.
Blue knob pulled back results in coarse pitch and max glide.
 
C/S control

C/S Prop control:
Forward: Flatens the pitch for take off, climb or slowing.

Back/out: Increases the pitch for high speed cruise/extended glide.
 
Another stupid question, if I want To slow down in circuit and move blue knob all the way forward, the engine's rpm will go up. Can it in any way damage the engine due to over reving? Same would apply in formation in a dive!
 
Moura said:
Another stupid question, if I want To slow down in circuit and move blue knob all the way forward, the engine's rpm will go up. Can it in any way damage the engine due to over reving? Same would apply in formation in a dive!
Click to expand...

You don't have to move it all the way forward. It still acts like a brake. In fact, if you move it forward too soon, it is like quick shifting into lower gear. Throws you towards the panel, and doesn't do well for the engine either. Just push all the way in on short final, when power is pulled back. I'd just usually leave mine, at the 2350 cruise setting. You'll only notice that the blue knob isn't full forward, if you do a go-around or touch and go. You'll notice a definate decrease in power.
 
Thank you L. But I was wondering what would be a reasonable / aceptable RPM in such a situation. Max. Take off rpm? Or could we go higher?
 
Moura said:
Thank you L. But I was wondering what would be a reasonable / aceptable RPM in such a situation. Max. Take off rpm? Or could we go higher?
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The max is set by the prop manufacturer, most Hartzell or Whirlwind compact is 2700 rpm red line. Allan
 
gov

actually prop rpm is restricted by prop manufacturer. Exceed rpm limits and it is a mandatory overhaul.
 
Max RPM

Also, Lycoming engine O-320/O-360 Max rpm is usually 2700, therefore many prop designs are same.
 
Not so fast...

paul mosher said:
actually prop rpm is restricted by prop manufacturer. Exceed rpm limits and it is a mandatory overhaul.
Click to expand...

Not quite. 2700 Max RPM on C/S props is correct for most manufacturers recommendations for certified applications and has carried over on experimental props sold to be installed on Lycomings. Being an IA I'm sure you know once you paste "experimental" on your type certificate, all bets are off. You don't have mandatory limits on anything per say, except your conscience, your posterior and the approved limits/maneuvers posted in the logbook during the test phase. If you follow certified standards and limits for your RV experimental airplane's engine/prop, good on ya. Years of testing, NTSB investigations and lawsuits have set the ultra-conservative limits on most parts sold by major aircraft parts companies. They do however perform very well beyond posted limits...

Even Hartzell likes racing airplanes and their custom made props for Dave Anders, the Reno Lancair Legacies and others have higher RPM limits (2900-3200) and were built specifically to run at higher RPM's. How are they different form a stock Hartzell? Call Kevin Karam at Hartzell, he'll tell ya. Craig Catto's background is Reno racing. His props come into their own around 2850 and "posted limits" up to 3200 for my 2 blade. Lycoming's limits running above 2700? That's another discussion for another day. Ask Mahlon, he's on the site.

FYI...

V/R
Smokey
 
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What is the maximum and minimum pitch of a c/s prop on a RV7 180hp?

Sensenich is fixed at 85 inches.
 
First Pitch...

gasman said:
What is the maximum and minimum pitch of a c/s prop on a RV7 180hp?

Sensenich is fixed at 85 inches.
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Gasman,
Weapons school answer: it depends...
Prop manufacturers measure pitch at different blade length percentages. Therefore 85 pitch on a Sensy may not be 85 on a Hartzell. My field experience has shown the 85 pitch Sensy coupled with a clean RV airframe will turn 2800 at 8500" 175 KTAS. The hartzells governed at 2700(unless you tweek it) so in effect you get a bit more top end, the Hartzell better takeoff. Personally I wouldnt remove the Sensy unless you operate off 1000" strips regularly. I would sell/trade for a Catto three blade first.

The extra 6-8 grand buys alot of 100LL.

My Dos Centavos
Smokey
 
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hartzell

From hartzell: 5. Special Inspections
A. Overspeed/Overtorque
An overspeed occurrs when the propeller RPM exceeds
the maximum RPM stated in the applicable Aircraft Type
Certificate Data Sheet. An overtorque condition occurs when
the engine load exceeds the limits established by the engine,
propeller, or airframe manufacturer. The duration of time at
overspeed/overtorque for a single event determines the
corrective action that must be taken to make sure no damage
to the propeller has occurred.
The criteria for determining the required action after an
overspeed are based on many factors. The additional
centrifugal forces that occur during overspeed are not the
only concern. Some applications have sharp increases in
vibratory stresses at RPMs above the maximum rated for the
airframe/engine/propeller combination.
(1) When a propeller installed on a reciprocating engine has
an overspeed event, refer to the Reciprocating Engine
Overspeed Limits (Figure 5-3) to determine the corrective
action to be taken.
(2) When a propeller installed on a turbine engine has an
overspeed event, refer to the Turbine Engine Overspeed
Limits (Figure 5-4) to determine the corrective action to
be taken.
(3) When a propeller installed on a turbine engine has an
overtorque event, refer to the Turbine Engine Overtorque
Limits (Figure 5-5) to determine the corrective action to
be taken.
(4) Make an entry in the propeller logbook about the
overspeed/overtorque event.

Can't get it to copy but figure 5-3 states any thing over 110% for 20 seconds requires evaluation by licensed facility. You do your own math.
I realize that in the experimental category you can do anything you want, but it doesn't pay to be uninformed.
I doubt that racing aircraft go to 2000 hours without a teardown.
 
Overspeed Warning!!!

---This is the over-speed statement in the Whirlwind manual that came with my propeller. I am sure they are using the standards set fourth by Hartzell so as to avoid any legal issues. Regards all, Allan :)
.
5.3 Overspeed Warning
It is possible to overspeed the propeller by rapid throttle
advancement. Therefore, always adjust the power and RPM
lever slowly and smoothly to avoid the possibility of
overspeed.
If an overspeed occurs:
Overspeed
Occurrence
Required Action
up to 110 % of the
max RPM
A 50 hours inspection must be
performed immediately by a certified
A&P mechanic
111% to 120% of the
max RPM
A mandatory teardown inspection at
the factory is required
above 121% of the
max RPM
No further use of the propeller is
permitted! The propeller must be
returned to the factory for inspection.
WARNING: Failure to adhere to these
guidelines may lead to a catastrophic
propeller structural failure. Any type of
structural failure may result in death or
severe bodily injury.
 
PerfTech said:
---This is the over-speed statement in the Whirlwind manual that came with my propeller. I am sure they are using the standards set fourth by Hartzell so as to avoid any legal issues. Regards all, Allan :)
.
...
A 50 hours inspection must be performed immediately by a certified A&P mechanic
...
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Do they need to be inspected every 50 hours? That's almost three times a year for me. :eek:

If that is the case, I'll stick with my FP Catto.
 
N941WR said:
Do they need to be inspected every 50 hours? That's almost three times a year for me. :eek:

If that is the case, I'll stick with my FP Catto.
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No Bill they don't, it says if you over-speed it to 110% you should look at it in 50 hrs. This info was copied from the Hartzell manual and was acquired by Whirlwind when they purchased the company. I know many people with this propeller (myself included) that run them far beyond the 2700 rpm with no problems what so ever. The composite blades are a fraction of the weight of aluminum ones and do not exert anywhere close to the forces on the hub assembly. The composite blades also do not resonate like the aluminum ones and do not suffer from the same rpm restrictions that plague aluminum propellers (even though they remain in the operations manual). I have investigated and can find no record of a composite blade failure on any C/S prop by any manufacturer. Even Catto, with the vast number of propellers he has created has never had a composite blade failure. We have run his props racing at 3400 rpm with never an ill effect. All this being said I don't think anyone need worry about a small over-speed occurrence with any composite prop. Thanks, Allan :D
 
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