Prop RPM Avoid Range Operation

[flyboy122]

Esteemed Experts,

I've been screwing around recently flying IFR approaches and maneuvers in my 170B. I have the Avcon 180 hp conversion with the Hartzell constant speed prop. That also means I have an operational limitation between 2000-2250. The problem I'm running into is that it seems like where the airplane is happiest flying on a nice long ILS also seems put my RPM right in that range. Doh!

Has anybody else run into this? What numbers/settings are you using for approaches?

Thanks,
DEM

[canav8]

Fly the approach with a different flap setting

[DaveF]

I run at the top of the yellow RPM arc and 20 flaps on the ILS. That puts me at about 85mph indicated, which seems to be a good speed. I have venturis, so I need to keep my speed up to maintain suction, but I also don't like flying an ILS too slow. I don't have any trouble slowing to landing speed from 85 at the middle marker.

[blueldr]

I don't see why your airplane can't be flown at 2400 rpm on an ILS approach. I had to borrow a friends C-170 for a "FUZZ ride" one time, It had a Lycoming and a Hartzel and I just left it set at 2400 for the whole ride. The FUZZer was somewhat upset and wanted to know why I didn't adjust my RpM according to conditions. I just told him that 2400 worked OK for me any time. He hated to do it, I think, but he passed me.

[hilltop170]

I agree with BL, no need to fly the approach at reduced speed. I fly all instrument approaches in the 170 clean at 100-110kt and do not reduce speed or add flaps until the runway environment is in sight. There is plenty of time to slow down on any approach I have ever flown from the DH or MDA. You can fly a more stable approach the faster you go, its easier to go missed, and ATC and other faster traffic will appreciate you blending-in instead of being a roadblock to following aircraft.

[JohnNielsen]

John's C170B w/ O-360 & MT Prop

The RPM Range restriction is in placed with metal props because of very strong, damaging harmonic vibration levels were the natural frequency of the metal prop matches one or more of the primary order vibration pulse frequencies of the engine. You may not feel it, but the prop surely does and it is very destructive to the prop. Natural (Wood) core composite props like MT Propeller have no natural resonance frequency and thus no RPM range restrictions....Wood is Good!! I love my MT Prop on my 170!

John Nielsen

[blueldr]

Not to start an argument with the above report, but I never heard of any RPM restrictions for either the FP or CS McCauley two bladed metal props I had on my '52 C-170B with the TCM IO-360 engine.
incidentally, the metal McCauley props also did not reqiire an annual inspection by a licensed pest control contractor for termite infestation.

[c170b53]

John whats your engine STC and STC of the prop? Whats the prop's length ? I'm tryinmg to avoid the weight of the dampner thks

[170C]

John, really nice looking 170!! Tell us about your fenders. That is something I would consider doing.

[counsellj]

[quote="170C"]John, really nice looking 170!! Tell us about your fenders. That is something I would consider doing.[/quote

Let's please try to keep this thread on topic. The fender discussion would be well deserving of it's own thread

Jughead

[170C]

Well excuse ME!

[blueldr]

What the hell? I thought the pilot lounge is where we go to shoot the you know what!

Does anyone know of any other C-170 prop other than the Hartzel that has na RPM limit range?

[ghostflyer]

HEY!! What's a fender? in my part of the world it's a mudguard on a car. Also a fixed pitch Sensenich has rpm restrictions also . I think it's only on our shakey 4 bangers has this issue. When on downward leg I am reducing power to bring the speed back [blue aircraft] to 2000rpm, then turning on to base its back to 1200rpm [ with some flap{speed brake} ]and a descent of 500 ft from a circuit height of 1000ft so turning on to final around 500ft and still at 1200rpm ,speed [ very hard with a blue aircraft] and descent is controlled by aircraft attitude and if a sink is encountered and a trickle of power is added and at the end of the runway a flair is induced and with the aircraft at a level attitude normally a good wheel landing happens. It's only when I have touched down that throttle is reduced to idle .

[Roesbery]

Many years ago I talked to a fellow that did a lot of flying off the California coast looking for sharks or some other fish and he needed to operate in the restricted rpm range to get maximum fuel endurance. He looked onto the background of the restriction and found that possible problems could happen only at a high mp. I do not remember the number, seems like it was in the 30 plus inches, but it was well above anything you would normally use at those rpms. Mostly another cover your butt restriction. Bottom line don't get excited about the rpm restriction.

[blueldr]

In view of the above comment, as I remember there seems to be VERY FEW C-170 aircraft thast are likely to pull over thirty inches of manifold pressure except maybe in parts of Death Valley, or the Salton Sea, in CA.