Cherokee Arrow III (1976) MAP questions

[awetzel]

I recently got endorsed in the Cherokee Arrow III PA-28R-201. When it comes to setting the power RPM & MAP, my instructors never really went over the table from the Pilots Operating Hand book.

Taught, Take off is Pitch Full Fine, Full MAP, then once off the ground it is both MAP 25/RPM 25. In the circuit they taught me on downwind it is MAP 21.9 and RPM 24 (Under carriage down), then turning base MAP below 15, RPM Full Fine, then bring the MAP up as required for power to touch down.

We went out to the training area (Steep turns, Stalls etc) up to 4500 feet using MAP 22.9 / RPM 24, and keep bumping up the MAP 22.9 every thousand feet you climb as it drops as the pressure drops off with height.

If there are some experienced Arrow pilots around on here, some of your experience and input would be much appreciated with power settings. (Personally I would sooner just follow the hand book table as it is much easier, it get a little confusing when the school never went near the power setting table from the POH.)

I have a mate who fly's a Mooney who helped me out with setting decent points (rule of thumbs for a given TAS and height to loose) when flying cruise as you cannot just close the throttle to lose height like the C172's, Warriors and Archers.

Thanks

Andy
<img src="smile.gif" border="0">

[Woomera]

Aussie Pilot

I'm moving this to Tech Log (where there is lots of other really interesting stuff) as you will get a better response there and as it doesn't strictly belong here.

Cheers
W

[X-dash8thrasher]

aussie pilot

what kind of waste-gate does the -III model have ?

I got about for a year in the non turbo -II model as a "green" cpl many moons ago.

[Islander Jock]

G'day Aussie Pilot,

You will find as many different opinions on the correct power settings to use as there are flying schools or engineers on the field. We own an Arrow II and the most popular teaching is that after takeoff and gear and flaps (if used) are retracted then 25" and 2500RPM are used for the climb. Then regardless of the required performance or altitude 23" and 2400RPM is stated as the power setting to use. This is to ensure that the so called "golden rule" of MAP not exceeding RPM is maintained. However, as you have pointed out, a closer look at the aircraft flight manual will reveal that this is not always the case. I don't have the Arrow II table here but from memory 75% pwr @ 2,000ft calls for 25" and 2400RPM.

Whilst the Mooney is a much more slippery aeroplane you can still apply good handling of the engine in the Arrow by planning the descent and reducing MAP by say 1" per thousand ft or every two minutes. Even greater reductions are not really going cause instantaneous cracking of cylinders (unless you close the trottle at 9,500 and descend at 150kts.) but in the interest of engine care, try and be as conservative as possible.

Listen to your instructors, talk to engineers and other experienced pilots and get their views on how they best handle the power settings.

Good luck with it.

[ 07 January 2002: Message edited by: Islander Jock ]</p>

[awetzel]

Hi X-dash8thrasher,

It's a 200 horse power engine, 4 Cylinder. It is a very good aircraft to fly.

Thanks

AW
<img src="smile.gif" border="0">
Similar aircraft to what I fly...<a href="http://www.geocities.com/CapeCanaveral/Hangar/2890/" target="_blank">Piper Arrow III VH-RQN</a>

[awetzel]

Hi Islander Jock,

Thanks for the information as it is very helpful.

It is a great aircraft to fly. I fly near Sydney, but there is not too many Arrows III's around this area, will search around for an experienced instructor or engineer next time at the air field.

Thanks

AW <img src="smile.gif" border="0">

[Checkboard]

Most, if not all, instructors use these settings simply because they only use the aircraft in the training area, they never actually go anywhere with it!

Some aircraft have the power setting table reproduced on the sun visor, which is really handy, if not photocopy it and stick it with your nav board, or clipboard.

I always used rule of thumb power settings in the training area, but on navs, I would use the power setting table. Pick the power you want to use (typically 65% or 75%). The setting that is best depends on the hire rate of the aircraft, and the wind at the time.

If you are hiring it "wet" (that is the rate includes the fuel) then effectively the club or company you are hiring from is paying your fuel bill, while you only pay for time - in this case use 75% cruise power to cut your costs.

If you are hiring it "dry", then you will find that 75% power is cheaper in anything greater than about 15 knots headwind.

Once you have decided your power setting, chose the lowest RPM on the chart, with the appropriate MAP. (This may be something like 24"/2200RPM.) This will result in the least noise, and greatest efficiency. If the engine is vibrating too much for comfort, use the next highest RPM setting.