Piper Arrow 180 Help

[VFR Transit]

I am having a few issues with the Manual and POH for the aircraft and hope someone who has experience on type can offer some advice.

I am flying a1969 Piper Arrow 1 (180hp) and the manual itself is VERY basic in what it provides, I have a long trip to undertake and am looking to get the best range/edurance out of her for the trip.

Can anyone offer some advice on power settings and leaning procedures to get the best fuel flow and of course get the most out of her in terms of speed.

Any help would be good as the internet is not throwing much up itself.

Thanks
VFR

[BackPacker]

The only advise that I can give you is that the performance figures in the POH of an aircraft that's older than you should be taken with a bucket of salt. Or more.

Fill up the tanks. Make a two-hour flight at the altitude and mixture settings you plan to use. Refuel and see how far the fuel flow and speeds are off. Rinse, repeat until you have a very good idea on what the aircraft is capable off in YOUR hands TODAY. Not in the hands of a test pilot 40+ years ago.

[172driver]

Google is your friend:

Piper Arrow | Cheerful Curmudgeon (http://cheerfulcurmudgeon.com/arrow/)

[VFR Transit]

Hey 172,

I searched and searched but did not find that link, thanks very much indeed.

BP,

I have a good idea from recent flights but not at the Alt I am planning to fly. My first leg is 4 hours long so will guage it from there on.

Thanks
VFR

[Shorrick Mk2]

Note that the Arrow in the link is a retractable gear, constant-speed prop one.

I fly a fixed gear, fixed pitch prop Arrow and it'll never *ever* cruise at 135kts @75%.

[Cusco]

Note that the Arrow in the link is a retractable gear, constant-speed prop one.

I fly a fixed gear, fixed pitch prop Arrow and it'll never *ever* cruise at 135kts @75%.

Blimey: That's a novelty: can you post a pic, please

Craig: I may be able to help you with the number of an ex-group member who now flies his own Arrow 180. If you like I'll PM you.

I'll check first to see if he's willing and able to help...........

Cusco

[P.Pilcher]

Backpacker's advice is the one you want then. NEVER believe what it says in such flight manuals as these give the best figures with a super clean aircraft with immaculate paintwork, a just run in engine and a test pilot at the controls. In real flight manuals, prepared for public transport aircraft, such performance figures are "factored" which means that they are made worse to reflect an aircraft in normal condition flown by an ordinary pilot.

Rememember the old adage:
There is always plenty of gravity:
How much fuel have you got?

Professional pilots use factored data to calculate the fuel that, including reserves, they need for a trip - then they always add on a bit extra!

P.P.

[Shorrick Mk2]

Never mind - I read "archer" instead of "arrow" in the original post...

[A and C]

You will have no problem in getting the Lycoming operators manual for the engine, that will give you a range of power settings vs fuel flow.

Then use these has has been outlined above as it is doubtfull that an aircraft of that age will meet the book numbers

Having said that a few years back I did an airtest on a very dog eared Aztec and the aircraft bettered the book numbers by a small margin.

[Pilot DAR]

NEVER believe what it says in such flight manuals

Well.... Not quite...

The "Flight Manual" is the gospel, as it is very likely FAA approved, and the result of flight testing in accordance with the design requirements. However, notice that in this case, it is rather informal looking (not printed by the marketing department), and lacks a lot of performance information? The Flight Manual is provided to preent the information which the FAA requires that the pilot has, and being airborne without that document is a no-no.

On the other hand, the "Owner's Handbook" (or other variations on that term) can be chock a block full of all kinds of useful information, sometimes of unverified origin.

I did certification test flying, and performance data gathering for a Twin Comanche. Similarly it has both an FM, and OH. The performance figures on the OH were extremely optimistic, which I proved by performance testing in accordance with FAA test techniques. One example was the climb rate in the OH, of 1400 or so FPM, where my equivalent condition results were more in the range of 800 FPM. There is no regulatory requirement for accuracy in documents other than the FM.

If it says "Approved", and it looks like someone official signed it, believe it, otherwise, yes, take with a bucket of salt. Telling the insurance company that you ran out of fuel, but the OH said you should have had lots, would be a weak argument.

More recent documents of this sort will have certain sections or pages indicating "Approved" where other pages are not so indicated. That means that you're trusting the company for those "not approved" pages, 'cause the FAA is not standing behind them.

[IFollowRoads]

I had an Arrow 180 for 10 years and about 1300 hours, taken mostly over Europe but with a scoot down to Marrakech,

'High speed' cruise is below 6000' at about 40-45litres/hour and you should be somewhere around 135KIAS. 6000' is the limit for getting 24"MP, above which fuel flow drops, getting down to about 30-32lph at FL100. Approx 38LPH was the sweet spot in mine for the FL55-70 range where you get the highest TAS.

4 hours is pretty easy with full tanks, assuming your W&B allows full (it won't with 4 pax and baggage!)

For leaning, just follow Deakin or Braly and you won't go wrong

There is (was!) a 'handbook' available with fuel flows and speeds in it, which is a small A5 jobbie (compared to the A4 CAA approved POH I had on the G-reg, which contained very little performance data)

Best range will be with a pathetic speed (about 105MPH/90KIAS IIRC) and something like 25lph, and you will have to hold the gear extension override up, best endurance I never really worked out, but would normally do holds at 110KIAS or thereabouts: just go up and see what the smallest fuel flow you can do to maintain straight and level - I would guess you can get it down to below 20lph as long as the injectors are reasonably well balanced.

Have fun

[VFR Transit]

All fantastic information and advice, thank you all very much indeed.

VFR

[FlyingStone]

Usually the best range in an aircraft with constant speed prop is achieved by flying with RPM set at some low value (2000-2200 rpm), full throtle (or maximum continuous manifold pressure, but it's best to fly at altitudes where full throttle gives you max. continuous MP or less to reduce pumping losses) and mixture up to 30-40°F LOP.

PM if you need max. continuous MAP for given RPM for Lyco IO-360.

[Pilot DAR]

(2000-2200 rpm), full throtle

It must be a very high altitude required to achieve this, without flying "over square" on the power setting in a normally aspirated engine. Just to be clear, for a normally aspirated engine, power settings where the number of inches in manifold pressure exceed the RPM in hundreds should be avoided, unless that power setting is recommended by the engine manufacturer. It is these power settings which allow detonation to occur, and probably your first indication of detonation will be the sudden power loss resulting from a hole melted in the piston. This kind of engine operation has prompted the saying that fuel is cheaper than engine repair.

Avoid flying with the power over square, unless recommended by the manufacturer.

As for lean of peak, my recent review of the Lycoming IO-390 engine operator's manual says this is not recommended. That's enough for me - I'll spend the money on the fuel instead!

[dublinpilot]

Just to be clear, for a normally aspirated engine, power settings where the number of inches in manifold pressure exceed the RPM in hundreds should be avoided, unless that power setting is recommended by the engine manufacturer.

"over square" is an acceptable power setting according to the Piper Arrow II flight manual (not sure about Arrow I).

[FlyingStone]

Pilot DAR: The maximum continuous MP chart, which is part of Lycoming O-360 (IO engines included) operation manual suggests that Lyco IO-360-B1E engine can be operated continuously at 25"/2000 rpm or 23"/1800 rpm. Oversquare or not, it's what the engine manufacturer approved.

[Pilot DAR]

Fair enough. I flew a 180HP Arrow I lots, but truthfully, never got into the Operating Handbook for the various power settings. I did fly the Arrow 4, and did fly it to the extremes of power settings for range, but that's a different engine, and was 25 years ago, so the details have faded.

[UV]

Oversquare or not, it's what the engine manufacturer approved.
Shall I be the first to ask?!!!

[Big Pistons Forever]

The whole "never fly oversquare" thing is a left over from the days of radial engines. The POH for every VP prop GA aircraft I have ever seen permits over square cruise power settings. The only POH I have close at hand is for a PA 60 (Piper Aerostar 600). It has normally aspirated Lycoming IO540 engines and the POH permits any MP up to 29.5 inches when the RPM is at or above 2400 RPM.

The way to hurt engines is actually the opposite. By that I mean operate with very high RPM and very low Manifold pressures, particularly at high altitudes where the low BMEP will potentially allow the rings to float and score the cylinders.

[IO540]

By that I mean operate with very high RPM and very low Manifold pressures, particularly at high altitudes where the low BMEP will potentially allow the rings to float and score the cylinders.

That, however, is exactly what you do when operating anywhere near the operating ceiling (http://i101.photobucket.com/albums/m74/peterh337/f200.jpg). Low MP, but max RPM to get the maximum "suck" to get as much fuel into the engine.

[Pilot DAR]

The way to hurt engines is actually the opposite. By that I mean operate with very high RPM and very low Manifold pressures

Obviously, high RPM at the extreme is not good for engines. However, generally, I do not agree with the foregoing. I have done Transport Canada authorized detonation testing on both the Continental IO-470F and IO-520D engines, while testing for approval to run Mogas.

It was required that I actually cause detonation in these engines at the outset of the test, to prove that I would detect it during the testing of the subject fuel. What I found for both of these engines, was that detonation could be caused on 80/87 Avgas, with a power setting of 2000 RPM, and 25" MP, while the engine was running very hot. I could repeat the detonation, with these conditions, at will.

Detonation takes time to occur. That time becomes available when the engine is turning more slowly. Increasing MP makes the engine work harder and hotter, which increases the risk of detonation. The faster you turn it, the less time is available for detonation during the compression stroke. Faster at a lower MP will give you the power of slower and high MP, but cooler. We downshift while towing a trailer up hill don't we? Same rationale, speed the engine up, lower the MP.

Interestingly, once the detonation I caused began, it was very hard to stop. Reducing power did not stop it right away, and the engine actually ran hotter for a minute or so, when I reduced the power. Though I did not damage the engine during these tests, I certainly cleaned off the piston tops well, indicating that detonation had occurred at a low severity. The pistons were replaced during the inspection which followed the testing.

Having reviewed a Cessna Cardinal RG Flight Manual I have, I agree that the IO 360 is approved to run over square. Obviously Lycoming has proven this is operation with adequate margin. They are the experts, so I will accept that - but I still don't do it. Watching the indication of detonation during my testing, and the temps running away on their own, has left me very cautious about running any engine hard, other than square or less. Maybe I'm being too cautious, and wasting some gas, but other than stuck exhaust valves, I have never experienced an aircraft engine drive train failure.

Sorry for the thread drift...

[riverrock83]

I have a SAB Bulldog reference card in front of me which includes 1800 RPM, MAP of 22.5 (which gives a nice 4.8 GPH - cruising around 90 KIAS) with a maximum setting of 1800RPM / 25Hg MAP. I only mention it as it has a Lycoming IO-360 engine. Probably best to stick to the handbook / manuals rather than using rules of thumb like "never fly oversquare" unless you don't have the manual handy...

[osmosis]

Pilot DAR, no thread drift, very good post. Any private pilots transitioning to CSU would do well to digest your post above.

I have a best range question, still in line with the first post. I once read that Charles Lindburgh was consulted during WWII in order to get more range out of single seat fighters at the time in and around the Pacific theatre. I'm sure he advised, and flew to prove it, that he applied very high continuous MAP (somewhere around combat settings) but with exceedingly low RPM; in other words very oversquare settings. If I remember what I read correctly, he achieved ranges not achievable before thereby opening up greater usability of such aircraft; but there was a penalty, and this is where my memory fades. One can easily speculate of course, but does anyone have knowledge on this?

[XXPLOD]

I don't think WW2 comparisons can really be made with the present. The technique might work, but then engine longevity was not seen in the same way it is today!

[smitn05]

Dependent upon temps/altitude etc, its best to fly off the EGT just lean of peak.

I would be wary of running 'just lean of peak' unless the aircraft was fitted with GAMIs and 'all cylinder' EGT monitoring. The standard Arrow EGT gauge is a single cylinder monitor taken from the hottest cylinder, so running just lean of peak means that one of the other cylinders could be running at peak.

Unless you have some spare exhaust valves with you I would suggest RoP operation unless you have the aforementioned GAMIs and a JPI.

Our Arrow 1 performs very similar to the figures provided in the previous weblink (we usually operate 24"/2400) and on a trip a few years back to the Canaries achieved the best endurance figures also.

[FlyingStone]

Even by running with an individual cylinder at peak EGT, you wouldn't be hurting your engine, provided the power is somewhere in range of 65% or below. Of course, 24"/2400 rpm gets you quite a lot of power (140HP in your case to be precise, +- few HP due to temperature deviation), which is actually over 75% and thus not even recommended by Lycoming for cruise power setting. You actually can't state that running at 24"/2400 rpm power setting (cca. 77%) gets you best endurance/economy/range/you name it. The best efficiency in normal-aspirated aircraft piston engine is achieved by running it WOT (wide-open throttle) and leaned somewhere to peak BSFC - depends on the engine, but usually somewhere from peak EGT to 50-70°F LOP. If you need maximum endurance, you would need to reduce RPM to some quite low value (2000, perhaps even 1900 RPM - if prop allows it), with throttle fully open. But if you need maximum range, you would fly pretty high, due to higher true airspeed, ability to achieve normal cruise power (60-70%) with WOT. Surely this is usually at least twice the altitude at which you will get 24" with WOT.

The problem with ROP operation is that it's actually not safer than LOP. If you look at the now famous (thanks to John Deakin) EGT/CHT/% power/BSFC/FF chart, you will see that the power and CHT curve (which are almost the same) have a smaller gradient on the rich side, which means that if you want to play it safe and get out of the critical area (50°F ROP), you need to push the mixture far in/forward, thus giving the engine much more extra fuel to put the EGT at 100-150°F ROP. But on the other side, if you want to play it safe on the lean side of the EGT curve, you only need to lean it a bit more (in range of 10-20°F), and the CHT will drop significantly, while the decrease in power output will be barely noticeable. So basically, you are giving the engine a little less fuel and getting the same (or lower) CHT than you would by pushing an extra gallon or two per hour through injectors.

On the topic of burnt valves: you can burn your valves even by running full-rich, since the combustion slows down on both sides of peak EGT (stoichiometric burn), the only difference is you'll be using a whole bucket of fuel while burning them if running ROP. Besides, usually the main reason for "burned" exhaust valves is running the engine to some obscene CHT - some people think that if Lycoming states that the CHT limit is 500°F this is to be used for normal operations. :ugh: