Flying tips and advice available if needed

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Killratio
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Re: Flying tips and advice available if needed

Post by Killratio »

Hoots wrote:Hi guys, a quick one hopefully, what oil pressure should I be seeing in flight? I tend to fly at 2600 rpm and zero boost (seems to work) but the oil psi is up around 50 to 60, does that seem high? The engine is 3 hours in and in beautiful shape so I guess it's not quickly doing any harm but I did wonder.
..

G'day,

The engine oil pressure will be largely independant of RPM. The oil will build to the "design" pressure which the engine driven oil pump is "designed" to deliver..ie that which is needed.

This pressure will then remain fairly contstant in any cruising configuration. The only time you will see large differences is due to temperature..the lower the temp, the higher the OP. The merlin is designed to withstand pressures up to some 300psi and to run at 60psi odd in flight. The gauge reads only up to 150psi. You can see from this that low oil pressure is MUCH more problematic. The Merlin will seize in about 1 minute if oil pressure fails.

On the high side, the only "dangerous" pressure will be seen with summer oil at very low winter temperatures..apart from that the Merlin is extremely resistant.

Anythng below 30psi in flight is very bad news and normally you dont want less than 45. But anything up to 80is fine. Higher than that "in flight" may indicate a gauge problem rather than a system failure.

Darryl
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Hoots
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Re: Flying tips and advice available if needed

Post by Hoots »

Great answer and explanation! Thanks mate :)
The more time I spend in this spit the more I love it.

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LoneWolf
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Re: Flying tips and advice available if needed

Post by LoneWolf »

I have a question about taxiing the Spitfire, I think I must be missing something because it feels wrong. After a while of what I would call a sensible taxiing speed the engine starts to choke a little and needs a bit more gas to clear it. Only problem is if I do that it wants to zoom off!

I'm running with:
Mixture - Rich
Prop pitch - Fine (I think that's it, it's pulled out backwards)
Throttle - Open just a wee bit

Should I be running with lean mixture am I putting too much fuel into the engine? Or and I running at the wrong RPM? Advice on this would be appreciated! At least temperature control is sorted now I updated Accu-sim to 1.5.1, was amazed that after I shut her down after a brief flight the engine was ticking as it was cooling down. Little details keep appearing and make it even more amazing every time I fly... can't get enough :D.
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whiic
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Re: Flying tips and advice available if needed

Post by whiic »

LoneWolf wrote:I have a question about taxiing the Spitfire, I think I must be missing something because it feels wrong. After a while of what I would call a sensible taxiing speed the engine starts to choke a little and needs a bit more gas to clear it. Only problem is if I do that it wants to zoom off!
Slowing down the taxi speed when approaching curves in the taxiway it's normal for the engine to run a little rough. You need to clear the plugs by applying throttle a bit occasionally. Because you can't shut the throttle completely for a longer period, you really have to start slowing down very early so that you can keep it idling at lower end of stable idle rpm range.

So, maybe try a slower taxi speed or at least anticipate and act pro-actively very early. It's a difficult compromise between adequate taxi speeds (considering poor cooling while at low speeds, and increased time spent if taxing slow) and the risk of hitting the curve at too high speed and not managing to slow down to it without use of brakes. My suggestion would be that if you take off from airports that have long taxiways, start taxing earlier but don't hurry when doing the taxi. Using low idle rpm. You can take your time taxiing that way, no need hurry to avoid overheat.
LoneWolf wrote:Should I be running with lean mixture am I putting too much fuel into the engine?
Impossible. You cannot move the mixture lever further forward (to lean) than your throttle is. You need at least 1/3 of throttle before you can lean out the mixture. The mixture lever is physically forced to stay in rich position at low throttle. (This however is not modeled in Accusim. But for authenticity, do use rich mixture until you get airborne. Running the engine with 1/3 throttle required to put it into lean, is way too much throttle to have a properly slow taxi speed.)
LoneWolf wrote:Or and I running at the wrong RPM?
Yeah. If your engine runs rough on deceleration and increasing throttle to clear it up launches you forward, you need to find some middle ground between the two. A single millimeter of travel on your throttle quadrant can make a difference here. A low throttle setting just above rough running that can be sustained and would still allow the plane to slow down when approaching corners. On a paved taxiway, the rolling resistance is very low, so the required throttle setting to allow the plane to slow down even at a modest amount of deceleration is very close to being too closed for running well. Because of this, you should probably taxi slower. If temperatures are an issue, start your taxi before you finish warm up. Do your warm-up while taxing to take-off position. It requires very little power to taxi, so there's really no reason why you can't taxi with a cold engine. You don't need to rev it at all.

__

I, myself, usually don't start taxi right away, even on airports with longer taxiways. I let it warm up to around 70 deg C before starting taxi, because this allows the taxiing to dissipate some heat away from the coolant (cold coolant wouldn't cool down) and I get my oil warmer by spending some extra time on the ground. For people who are just getting used to Spitfire, I'd recommend starting taxi earlier so they don't need to hurry with the taxi. You may have a bit lower oil temperature (and thus higher oil pressure when taking off) if you do your warm up while taxiing to take-off position but this is usually not a problem since it's normal for oil pressure to go off-the scale during take off. 15 deg C oil temp is absolute minimum and 30 deg C is highly recommended. Reaching 30 deg C is usually achievable even without any special tricks so feel free to taxi with a cold engine when in warm or mildly cool weather.

In cold weather, you may want to warm up stationary because likelihood of overheating is significantly reduced and even slow taxi speeds are adequate to cool down the engine. Starting taxi only after your engine coolant has risen to normal operating temperature (i.e the thermostat valve that blocks coolant flow to the cooler has opened) can give you an extra minute of warm-up time. It of course depends on the length of your taxiway.

In very cold weather, or when you have no taxiway to use and have the plane in take-off position, you can consider starting the engine and shutting it down via normal shut down procedure once the coolant temperature has hit about 100 deg C. Let it cool down and restart (coolant cools down faster than the engine), and you get a second warm-up.

francesco.doenz
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Re: Flying tips and advice available if needed

Post by francesco.doenz »

Hello Dudley,
I need your advice again!
After many weeks of training the takeoff with the Mark one two-blade, I am now convinced that after an initial left-turning tendency at takeoff, the plane has a definite tendency to pull to the right when it gathers speed on the runway?!
Up to now I was thinking the expected deviation should be to the left (Machado's book!) and I am guessing why it has at the end of the runway the tendency to stray to the right? Software bug? Faulty handling? Drag of the cooling radiator?
Looking forward to your opinion!
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DHenriques_
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Re: Flying tips and advice available if needed

Post by DHenriques_ »

francesco.doenz wrote:Hello Dudley,
I need your advice again!
After many weeks of training the takeoff with the Mark one two-blade, I am now convinced that after an initial left-turning tendency at takeoff, the plane has a definite tendency to pull to the right when it gathers speed on the runway?!
Up to now I was thinking the expected deviation should be to the left (Machado's book!) and I am guessing why it has at the end of the runway the tendency to stray to the right? Software bug? Faulty handling? Drag of the cooling radiator?
Looking forward to your opinion!
I know it's not the flight model or a bug as I haven't had the issue during testing.
Try looking at your rudder in outside view to see where it is positioned during the issue.
Check your trim setting and make sure that it's correct.
Check controller calibration.
DH

francesco.doenz
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Re: Flying tips and advice available if needed

Post by francesco.doenz »

Thanks Duddley for your methodological approach, I checked all the points you mentionned in your response and it was a faulty calibration!
Have a nice day!
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FS20
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Re: Flying tips and advice available if needed

Post by FS20 »

Could someone please point me in the right direction when it comes to descending? Flying the MK11b constant speed prop.

AshtonPete
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Re: Flying tips and advice available if needed

Post by AshtonPete »

For a week now I have been getting off the ground properly in the Mk2b, I have flown as far north of England until I got a bit bored, all checks in order, temp correct etc.
But tonight for some reason the plane is shaking/vibrating badly, it gets so bad it loses altitude and smashes into the ground.
Any ideas what's gone wrong all of a sudden? Its got me flummoxed. Oh yeah, its also vibrating whilst stationary warming up. :(

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Lewis - A2A
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Re: Flying tips and advice available if needed

Post by Lewis - A2A »

Hello Pete,

Hows the aircraft maintenance wise, all OK in the hanger?

thanks,
Lewis
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AshtonPete
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Re: Flying tips and advice available if needed

Post by AshtonPete »

Indeed it is, I covered all, did compression checks. One thing I didn't do, change the prop, but it made no difference for the past week. :) I'll try that now.

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Lewis - A2A
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Re: Flying tips and advice available if needed

Post by Lewis - A2A »

How's your FSX settings? Are they still set as per the manual?

Thanks,
Lewis


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ubiquitous
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Re: Flying tips and advice available if needed

Post by ubiquitous »

I am still getting the hand of the spit and was curious about the best strategy for handling the following scenario: often, if taking off from a large airport, the taxi from parking to runway is long and the engine is close to overheating before takeoff. In these instances, ehat is the best strategy for managing engine temperature? Do you need to fly low and slow until the temperature drops, or is it ligitimate to put on a lot of throttle to build speed in the hope that this helps you to cool the engine more quickly? How does one strike the balance? Or is the best strategy in these cases to shut off the engine once on the runwat and start again after tempteratures have normalised?

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Lewis - A2A
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Re: Flying tips and advice available if needed

Post by Lewis - A2A »

Fly with speed and get high, if possible don't fly from larger airports the aircraft is modeled as it was in WW2, its designed to be started and go, anything over 5mins taxing and wondering around on the ground is going to cause some issues if its a warm day.

thanks,
Lewis
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ripvan
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Re: Flying tips and advice available if needed

Post by ripvan »

Hope I'm not interrupting.

What might be best method for transitioning from lean cruise low rpm, to app/landing config?
(full rich, prop full forward, boost down)

ie, Trying to achieve smooth transition in the rpms on approach/landing when "swapping" back from lean cruise.



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