Different power settings (Arrow)

[a-v-8er]

Why would you choose one power setting (that gives you the same performance) over the other when flying an Arrow?

The POH specifies two different MP/RPM settings to get the same rated power, TAS and fuel consumption.

For example 25"/2100 and 22"/2400 would give you the same results at a certain altitude. Now, what would be the con's and pro's for using either one?

Engine wear, noise, vibrations? Why would you pick one over the other and why does the POH give you that option?

 

[bigD]

Usually vibration is a big issue for me. Sometimes a specific MP/RPM combination will create an uncomfortable vibration, so I pick a different one. I've found that even different planes of the same model will have different power settings that result in the least amount of vibration.

 

[midlifeflyer]

You'll find that most (all?) constant speed prop aircraft have multiple combinations that produce the same performance.

The manufacturers tend to recommend the combination that gives you the least vibration and lowers noise level.

See http://www.lycoming.textron.com/mai...ions/keyReprints/operation/powerSettings.html

This tends to be the highest manifold pressure and lowest RPM on the chart, but not always.

 

[Ralph]

Unless its a 3 blade prop you can only pull the RPM back to 2350 in an Arrow as a result of vibration issues. I assume you also mean a normally aspirated arrow (not turbo charged)

I've flown an arrow for at least 100 hours and I can say the best power settings are as follows.

Take off: Full throttle, max RPM

500ft AGL: Full Throttle, 2500 RPM

Cruise: Full throttle, 2350 RPM

Descent: Full throttle, 2350 RPM

In other words... Full throttle

Somewhere someone will tell you never run it over square. Thats bunk, run it over square. Unless the yo-yo owns the plane, then run it 2500 squared everywhere, never put the flaps in while turning, and remeber you need power in to land.

 

[rfeathe1]

Lower RPM settings= less fuel burn because there is less internal friction to overcome.

 

[Wiggums]

Also, lower RPM = less engine wear.

 

[bobbysamd]

Power settings

I second the above comments. I've also heard that a higher RPM is better in rough air.

I believe the over-square argument is an old wives' tale that comes from radial engine operation. You are not supposed to overboost a radial - but you can with an opposed 4, 6, etc.

 

[rfeathe1]

I don't think the old wives tale about running them over square came from radial engines. Every radial I've flown had power charts that showed cruise power settings way over square. 2100 RPM & 32 inches was typical at 10000' I really don't know how that story got started but it's been around for at least 45 years.

 

[Cardinal]

never put the flaps in while turning,

Out of curiosity, why this assertion? I'm completely willing to accept it, because Pipers are just different. I spent 50 begrudging hours in a Arrow III, cross-country and dual given and never really noticed anything in this regard. Perhaps I was distracted while screwing with the sunvisor and airvents for most of that time. Care to enlighten us?

As far as power settings, full throttle and any comfortable RPM is indeed the way to go.

 

[U-I pilot]

the reason i heard for not putting down flaps while turning is incase of asymetric flap deployment....because it is manually done versus the slow moving electric, lift changes quickly and therefore could flip you if you werent ready for it....
any other explainations?

 

[Ralph]

Assuming you fly coordinated.... what’s the difference between putting flaps in during a turn and putting them in while straight and level?

Now perhaps if you are turning base at the critical angle of attack with the aircraft uncoordinated, and you had an asymmetric flap deployment at the same time... you'd eat it, but then the problem was not really the flaps, its that you were flying at the critical angle of attack with an uncoordinated airplane and very close to the ground. I'd argue that those ingredients alone will spin you into the ground.

 

[bobbysamd]

Flap extension

I, too, have plenty of hours instructing and I never experienced a bad flap extension. I trained students in several aircraft, ranging from Cessnas to Pipers to Mooneys to Bonanzas to Barons. I never heard of not extending flaps during turns, either.

 

[jetdriven]

I had a friend who worked at texas air who was flying a C402C, and while on a tight left base he extended the flaps from 30 to 40. at that same time the left flap torque rod broke and the airplane flipped over inverted at about 400' AGL. His hand was still on the flap lever so he put it full up and it took full aileron to recover. So, it can happen.

I cant get any reciprocating engine in these small airplanes to run smoothly below 2350 RPM. The airplane will always run better at full throttle and 2400 or 2500 RPM. Turbo 210's, senecas, 402's, PA31-350's and similar like 2350 RPM and "top of the green" MP.

 

[rfeathe1]

Never putting flaps down while turning is another old wives tale (first time I've heard that one) along with never turn downwind close to the ground, never enter an overcast in a turn, never fly IFR in a single engine aircraft & numerous other admonishments I've heard over the years.

 

[bobbysamd]

One more old wives' tale

Never putting flaps down while turning is another old wives tale (first time I've heard that one) along with never turn downwind close to the ground, never enter an overcast in a turn, never fly IFR in a single engine aircraft & numerous other admonishments I've heard over the years.

And don't forget about the one about not turning into the "bad" engine in a multi during single-engine ops.

 

[Mr Proach]

Whilst doing a recommended search for Arrow II info, I find this thread interesting.

Recovering from a asymmetric flap extension, if the wrong wing is affected in the turn, followed by opposite aileron, on say the base to final (slow) is getting quite close to a flick roll????

I always subscribed to the electric flap idea (not in a turn) and also believe that less manouverable a/c should have plenty of warning (i.e. they couldn't produce 180 deg roll in 0.4 seconds), BUT: why test fate????

Boy this stuff is fun huh!?

 

[A Squared]

You may have noticed that in a moderately banked turn, your ailerons are approximately neutral. (don't they teach this stuff in flight schools anymore) If you con't have enough aileron authority to maintain control of an asymetric flap extension with your ailerons neutral in a turn, you don't have enough aileron control to maintain control of an asymetric flap extension in level flight.

regards