REFLECTOR: Reflector: Propeller Feathering

Wed Jun 20 15:07:50 CDT 2012

I may be misquoting but if I remember correctly Velocity has said in their testing showed this prop wasn’t as efficient as the MT. Of course I’ve also heard them say the same thing about the AeroComposite but have heard otherwise from AC owners. I’m sure there wasn’t any prejudice, Velocity being an MT dealer and all.

Best regards,

Nick and Connie Jones
Velocity XL-RG
N10CN
99% done 90% to go

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of flykb at verizon.net
Sent: Wednesday, June 20, 2012 3:58 PM
To: reflector at tvbf.org
Cc: reflector at tvbf.org
Subject: REFLECTOR: Reflector: Propeller Feathering

 Hi All,
Almost got one of these a while back - but was unsure about the feathering or who was running one.

This is the propeller Hoffman.
http://www.hoffmann-prop.com/index.php?id=15

HO-V 123

Constant speed propeller,

hydraulically controlled

The propeller HO-V 123() is a three bladed single

acting fully hydraulically controlled constant speed

propeller. The hub is made from forged aluminium

alloy to fit to the Lycoming, Teledyne engines, but

different flanges are also available. The blades are

wood - composite with FRP-covering and leading

edge guard.

The pre-selected propeller RPM will be kept constant

in the normal operating range by a propeller governor.

This propeller uses oil pressure to increase pitch.

The travel of the propeller blades is limited by

mechanical stops.

In the event of an oil pressure failure the propeller

blades automatically return to the low pitch stop and

the propeller can be used as a fixed pitch unit.

The propeller RPM has to be adjusted and controlled

by the throttle only, but the flight may be continued.

For special applications the propeller uses oil pressure

to decrease pitch. In this case counterweights

have to be used to turn the propeller blades towards

coarse pitch. In the event of oil pressure failure the

propeller blades automatically go to the high pitch

or feathering stop.

P max 239 kW

n max 2800 1/min

Number of blades: 3

Diameter max.: 90 inch

Pitch change range: about 115 deg

Weight: about 55 lbs

Weight of the spinner: about 3.75 lbs

Polar moment of inertia: about 6500 lbs in 2

Governor: Woodward 210xxx Serie,

McCauley, Hartzell, Jihostroj

m HO-V 123

The propeller HO-V 123()-S is a three bladed

single acting fully hydraulically controlled

constant speed propeller with feathering

position.

The pre-selected propeller RPM will be kept

constant in the normal operating range by

a propeller governor. This propeller uses oil

pressure to decrease pitch and counterweights

and a spring force to increase pitch

till feathering. In the event of oil pressure

failure the propeller blades automatically go

to the feathering position. The travel of the

propeller blades is limited by internal

mechanical adjustable hard stops.

To un-feather the propeller during flight a

hydraulic accumulator, which stores oil

under pressure is needed. This oil supply

is released to un-feather the propeller.

The propeller starts to windmill and engine

restart is possible.

To prevent feathering during normal engine

shut down on the ground the propeller is

equipped with a spring loaded start lock.

To disengage the locks the static RPM has

to be at least 700 RPM or above.

The following data are only standard

values. For installation purposes only the

data given in the applicable Type Certificate

Data Sheet (TCDS) No. 32.130 / 17 of the

German Luftfahrt - Bundesamt (LBA) are

valid.

Type certifications: FAA - P5EU.

On 06/20/12, Kevin Baker<flykb at verizon.net> wrote:

Ahhhh I wondered about that.
Very good explanation

I love all the knowledgable folks here on the Reflector.

I learned yet another thing today :-)

Thank you
Kevin Baker

.

On Jun 20, 2012, at 10:05 AM, Mark Magee <edjonesbrady at gmail.com<mailto:edjonesbrady at gmail.com>> wrote:

> Hi Kevin,
> FULL FEATHER is best case scenario for any propeller driven aircraft that has lost power. We don't see it available so much in GA because it can require a hydraulic pressure reservoir. With a dead engine the windmilling is now the power source that turns the oil pump that controls the prop pitch. As pitch approaches FEATHER prop drastically slows down, as does oil pump, as does oil pressure required to continue pushing the blades to FEATHER. With no oil pressure reservoir (large and heavy) getting that blade those last 20-50 degrees to FEATHER becomes impossible as their is no more oil pressure left to push the hub. This is all assuming you haven't bled out your oil. Commercial turboprops will most likely have a hydraulic reservoir to get to feather, which will be the least drag/best glide or single engine performance profile.
>
> Mark B. Magee
> N34XL XLFG
> Sent from IPhone 4
>
> On Jun 20, 2012, at 9:41 AM, Kevin Baker <flykb at verizon.net<mailto:flykb at verizon.net>> wrote:
>
>> So to add to that thought..
>> What about the props that go to full feather when the engine quits...
>> I seem to remember a cs prop mfg that does that.
>>
>> Thanks
>> Kevin Baker
>>
>> .
>>
>> On Jun 20, 2012, at 8:11 AM, Brooke Wolf <bwolf1 at tds.net<mailto:bwolf1 at tds.net>> wrote:
>>
>>> Not an expert Don, but I think you are right (others please chime in). When you are out of oil you are SOL. You are going to be landing closer to current position because without oil pressure, your prop resorts to fine pitch resulting in more drag. But don't worry too much���.spin that prop too long with no oil and you will end up with a stopped prop. Less Drag! Isn't that swell :>) That is a good question about windmilling in course .vs. stopped in fine. Don't know the answer.
>>>
>>> Brooke
>>>
>>>
>>>
>>>> There's one point missing from this conversation:
>>>>
>>>> There are a lot of ways an engine can fail. Pulling the prop control back to improve the glide is only going to work in some of those failure modes. On an engine with a non-electric prop governor, pulling the prop control back is only going to help if A) there is oil in the engine and B) the engine is turning. If the failure is a result of no oil or the engine isn't turning, pulling the prop control back won't affect the prop.
>>>>
>>>> Which then brings up the topic of what is the drag difference of a stopped prop in fine (control forward) mode vs. windmilling in course (control back) mode?
>>>>
>>>> Now discuss. :-)
>>>>
>>>> -Don
>>>>
>>>>
>>>>
>>>
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