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-   -   I Don't Get It - FP vs CS (https://vansairforce.net/community/showthread.php?t=80855)

smokyray 03-07-2012 10:09 AM

First Pitch...
 
Quote:

Originally Posted by gasman (Post 636988)
What is the maximum and minimum pitch of a c/s prop on a RV7 180hp?

Sensenich is fixed at 85 inches.

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

RV6airplanePilot 03-07-2012 10:27 AM

Hey
 
Quote:

Originally Posted by paul mosher (Post 636025)
actually prop rpm is restricted by prop manufacturer. Exceed rpm limits and it is a mandatory overhaul.

That is not very precise; 2750 for example is not cause for an overhaul. Paulie, are you smoking again? (read your profile) :rolleyes:

paul mosher 03-07-2012 11:16 AM

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.

PerfTech 03-12-2012 11:47 AM

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.

N941WR 03-12-2012 12:12 PM

Quote:

Originally Posted by PerfTech (Post 638853)
---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
...

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.

PerfTech 03-12-2012 12:54 PM

Quote:

Originally Posted by N941WR (Post 638861)
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.

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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