Flying turbo SEPs

[ThePirateKing]

Hi all,

Having flown PA28 Warriors and Archers for several years, I am considering converting onto the Arrow. (I've done the conversion training before, but the club a/c was landed wheels-up the week after, so I've never actually flown it solo! :\ )

My current club has a turbo Arrow, so I'm interested in knowing what difference flying a turbo makes? What different procedure are there, etc.?

Many thanks,

TPK:ok:

[FlyingForFun]

(I've done the conversion training before, but.....)TPK, I assume from your post that the Arrow you did your convertion on was not turbo-charged?

Sure there are plenty of people on these forums who can give advice on flying turbos. Have to admit that the only turbo-charged a/c I've ever flown is my Europa, and that handles almost everything automatically, so I'm probably not the best person to give advice on the more normal turbo-charged a/c.

However, from a legal point of view, you must undergo differences training for a turbo-charged aircraft if you've not flown one before. That will, at the very least, include a thorough ground-briefing, and almost certainly will also include some flying with an instructor. You probably knew this already, but I thought I'd point it out just in case!

FFF
------------

[deice]

Can't specify exactly what your procedures would be but Turbos generally require you to monitor Manifold Pressure on the take-off run. If you overboost the turbo you ruin the engine. You also need to keep an eye on the turbine inlet temperature.

I'm pretty sure the Arrows Turbo installation does not have a wastegate limiting your MP to the allowed max and therefore increases workload. Typically, you add power to a limit dependant on pressure altitude and temperature. As your airspeed increases during takeoff so does your MP and hence you may need to back off on the throttle.

Most pilots I would assume will set a "safe" MP and then adjust as they build speed without fiddling too much with it.

The problems that may arise are if you need to abort a landing and go around, add power gently. Also, coming from high altitude you may need to back off on the throttle in order to maintain a safe MP.

My friend has a Commander 112TC and he eats up alot of runway due to feeding in power slowly. He pays the bills so I'm not arguing.

Apart from keeping the MP in check it's a plain old Arrow. Oh, you'll need oxygen if you want to use it to the full extent.

[dirkdj]

If you google 'John Deakin Fire breathing-turbo' you will find a wealth of information about handling turbocharged engines. I haven't seen any better so far.

[IO540]

I think that J Deakin should be mandatory study material for anyone flying anything bigger than an IO-360, or anything with a turbo :O

However beware of general advice. I know little about turbos (no need to know, as yet) but I do know that installations vary, and in some installations turbo mis-use can wreck an engine very quickly (minutes or less). So beware of any generic advice, no matter where it comes from.

[ThePirateKing]

All,

Thanks for the advice. All very useful.

FFF: I will, of course, do the differences training (again). I just wanted to get a handle on how much extra workload there will be (having never actually flown wobbly legs and a wobbly prop solo).

Rgds,

TPK:ok:

[dirkdj]

IO540,

My experience with turbocharged pistons is limited to the TIO541, TSIO360 and the TN-IO550 but the principles John Deakin explains are valid for all engines. If there are differences between his writings and the airframe manufacturers manuals, I would be inclined to go with Johns version unless proven otherwise.

There is some wrong advice in several 'approved' POH out there. POH information is written by engineers, edited by the marketing dept, and final edited by the legal dept.

[High Wing Drifter]

Hi PirateKing,

Only recently started in the turbo Arrow at, no doubt, the same club as you ;)

The turbo particulars that I find tricky are:

* Quickly selecting t/o power without overboosting!! You don't just go full throttle, shouldn't exceed 39" and mustn't exceed 40". This compounded by the procedure to select 34" after wheels up. I'm much too heads down at the moment.

* The thottle adjustment seems to have quite a bit of a built in latency and requires a little anticipation and micro adjustments to get within and inch of pressure. You think you have it and glance down a few seconds later to see that you have dropped 3" I have found myself getting a little fixated with that.

The first aircraft I have flown where you can actually feel the acceleration :D

[Tinstaafl]

It's not the throttle mechanism. The lag is because of the time taken for the turbo to spool up or down as the mass flow through the exhaust changes. The sequence is:

Open the throttle --> more airflow through the engine (and more power output of course) --> more flow through the exhaust --> turbo begins to spin faster --> the compressor begins to spin faster too, causing more mass flow through the engine --> some more inches HG added.

Eventually it stabilises at a setting.

After a bit you'll get an idea of how many inches Hg change to expect then you'll be able to set a power setting that allows for the expected change. How much depends on how large a power change you're making. Afterwards only a small adjustment is normally required to fine tune the power setting. Slow movement of the throttle helps with the adjustment.

Adding power I set a couple or few inches less than my desired setting which allows for the spool up. Reducing power I set a couple or few inches more than the desired setting to allow for spool down.

[tom775257]

Just a thought. I wouldn't reduce power at gear up. Power reduction will increase the chances of engine failure. Yes gear up when out of usuable runway. Personally I wouldn't touch the power until 1000' AGL or so - at least you have a good chance of getting into a field if the donkey quits. And you are not distracted head in cockpit during a very critical phase of flight close to the ground.
Correct POH performance take off technique in the turbo arrow is holding on the brakes, and set 40" before brakes release. Do you really want to be messing around with power during the take-off run when not really necessary? It is less safe, and invalidates the performance graphs. It is a shame schools teach non POH technique to save money on Mx.

[High Wing Drifter]

Tom,

Re t/o power, its more an issue with touch and goes IMHO. I couldn't accuse my school of skimping on training to save money :)

[tom775257]

Yeah I agree on the touch and go issue. Pain in the ass having to set flaps, T/O power etc. on touch and go in the turbo arrow. But I do not see why on a normal take-off we shouldn't have the added safety of not having to set power on the roll.

Just for general interest for TPK: on the turbo arrow there is a simple device to limit manifold pressure. A spring loaded pressure relief valve prevents more than, if memory serves, 41" of pressure into inlet manifold. Any excess air is dumped over board. So although you may have an overboost indication, if everything is working correctly, you shouldn't damage the engine. The problem is with an overboost setting, more air is being compressed that necessary, so the air is hotter than necessary....this leads to reduction in power output and possibly engine problems eventually. Say on a go around IMHO it is better to have a mild overboost for a short period of time than set too little power due to fear of the overboost.

[ThePirateKing]

HWD,

Did you ever meet M14P for that curry? ;)

My other worry with this particular Arrow is that it's a t-tail. When I did the differences training previously, it was on an aircraft with a regular tail/stabilator.

Any time you'd like some company, give me a shout.

TPK:ok:

[High Wing Drifter]

Tins and Tom,

Thanks for the feedback and advice. I shall consult with my instructor next lesson.

PirateKing,

I don't know if this is specific to the T-tail, but it is one hell of a brute on the elevator. After doing stalls my left arm just wanted to fall off!

As for M14P, very nearly. I'm sure our diaries will be compatible at some point in the next couple of years :) I'll drop you a PM when we finally get our holy grail of a prop; the damn thing went in for its Star Annual in October...its still there :{

Soon...hopefully :ok:

[Tinstaafl]

There's another factor at play that I completely forgot to mention: variable pitch or CSU props.

As you reduce RPM you will see a rise in MAP. If your power reduction will include an RPM reduction too then you will probably have to set MAP an inch or two below you're intended final MAP setting.

[tom775257]

Hi Tinstaafl.

Sorry to be picky but I find the opposite from what you say on the turbo arrow and seneca II (same engine).

Here is a quote from my Seneca II guide re: VP props and MAP:

"There is an oddity in MAP/RPM relationships in connection with the fixed orifice turbocharger. In a normally aspirated, VP prop driven aircraft, when a pilot wishes to decrease power when he reduces RPM, the MAP with increase slightly. The opposite happens in the Seneca II (also turbo Arrow - same engine) where a decrease in RPM causes a decrease in MAP because mass flow through the turbine decreases" etc. etc.

All the best, Tom.

[Stan Evil]

tom's quite right - with the Seneca II, III and Turbo Arrow installation you tend to go from climb at around 34" and 2400 or 2600 to cruise at 30" and 2200 or 2400 just by bringing the props back - the turbo slows and the MAP drops nicely to cruise power. Although Mr Piper has put a 'safety valve' on the installation I've not seen one yet that limits boost to 41" - if you firewall the throttle you'll probably see 45" or 46" (but not for long!!). So get used to the throttle position for about 34" - go to that on a go around or stall recovery, wait a sec or 2 and then tweak it to what you want. That said, Overboost Light on for a second or 2 won't hurt as long as you then do something about it - it's better than setting less than 30" and not recovering from the stall, UA, engine-fail in a Seneca etc.

As far as the T-tail is concerned it's probably more good news than bad. The stall recovery is hard work but think about what you've done with the trim running into the stall. In a Warrior, say, there's only 40 kts between cruise and stall. In an Arrow it's more like 60 kts; so, if you don't retrim once you've closed the throttle for the stall you'll have to pull very hard. Try trimming down to, say, 80 kts and see if it's any easier.

Where the T-tail helps is when lowering flap - much less trim change than a conventional tail as it's out of the wing downwash. On landing too, you don't get a sudden loss of authority as you close the throttle in the flare - much easier to grease on than a conventional Arrow.

Have you noticed the funny, upside-down slots on the stabilator - ask your FI what they're for!

[High Wing Drifter]

Tom and Stan,

I had noticed lessened trimming once I stopped trying to use the electric trim that seems to take forever. I'm going to watch for the MP effect much more closely next time out. Great feedback. Thanks guys.

Have you noticed the funny, upside-down slots on the stabilator - ask your FI what they're for!
I have noticed and haven't asked yet. But as a guess...

Are they to keep a flow of air below the tailplane at high angles of a attack to maintain authority for longer because of the blanking effect of the wings in such an attitude?

[Tinstaafl]

I think I should have used 'could' instead of 'probably' in my last post. I've flown a number of turbocharged a/c & each type has been slightly different in its MAP reaction to throttle movement & RPM changes.