Recommended Posts

The POH for this type describes four tanks - Inboard & Outboard per side. My question is how are the outboard quantities indicated? The aircraft.cfg looks like all four tanks are modeled. I suspect it is all grouped together simply as Left & Right. I can't find ther answer in the real world POH either.

 

Thanks / Les Parson

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

Your assumption is correct--the tanks are grouped together as left and right.  There is no indicator for the outboard tanks as far as I know.  I personally set both fuel tank switches to inboard and leave 'em there.

Share this post


Link to post
Share on other sites

Carenado modeled left and right tanks, both auxiliary and main, but used the stock MicroSoft fuel management system which drains from the auxiliary tanks first, regardless of where you set the fuel selector.  Carenado also modeled the fuel gauges so they show total fuel in the left and right wings, not in individual tanks.  I'm not sure if this is correct or not.  FSD modeled their FS9 Piper Navajo/Panther to show fuel quantity in whichever tank was selected. 

Share this post


Link to post
Share on other sites

Thanks for the info. I think the Carenado C340 fuel system was modeled correctly, but I know that won't help the PA31 since we know Carenado won't correct it. 

Share this post


Link to post
Share on other sites

Hey guys! Actual former PA-31 pilot here. I saw this topic and thought I’d fill you in on the fuel indicator.

The way FSD modeled the indication is correct. The X-Plane model by Carenado is also correct, or at least the Navajo version of it that I have is. The gauges in the real airplane show the quantity in whichever tank is selected. Also, the normal procedure is to take off on the inboard tanks, then switch to the outboard tanks for climb, cruise, and descent. Make it a priority to never let the inboards empty before the outboards. Also in real life you want to turn on the associated fuel pump when you change tanks or the engine will usually start a nasty bout of surging before the fuel flow stabilizes.

Passengers didn’t particularly enjoy this indication system on the Navajo as they would get worried watching the fuel gauge dip to zero on the outboards long before the flight was over. Made them very nervous. I believe the Pressurized Navajo and Cheyenne had individual tank indicators, but I’m not sure.

In Navajo passenger service, you really wouldn’t want to run the tanks all the way dry before switching. Maybe switch with a minute amount of gas left in the tanks. The L/R fuel pressure or fuel flow (I can’t remember which) annunciator would go off, indicating fuel flow was getting weak from the almost empty tank and you had 5-8 seconds to switch. In reality it was more like 3 seconds. If you were distracted in hard IFR or had your hands somewhere else in the cockpit and missed the warning light, the engine would start bucking and surging like crazy until it either died momentarily or you switched to the proper tank. Not a problem in cargo, which I flew.

Hope this has been somewhat helpful. Good choice of airplane! I loved the Navajo (although I flew the larger Chieftain). I miss flying it, but greater opportunities came along in my career. Now I relive those days at home.

  • Upvote 2

Share this post


Link to post
Share on other sites
On 1/26/2018 at 0:08 PM, StarvingPilot said:

Hey guys! Actual former PA-31 pilot here. I saw this topic and thought I’d fill you in on the fuel indicator.

The way FSD modeled the indication is correct. The X-Plane model by Carenado is also correct, or at least the Navajo version of it that I have is. The gauges in the real airplane show the quantity in whichever tank is selected. Also, the normal procedure is to take off on the inboard tanks, then switch to the outboard tanks for climb, cruise, and descent. Make it a priority to never let the inboards empty before the outboards. Also in real life you want to turn on the associated fuel pump when you change tanks or the engine will usually start a nasty bout of surging before the fuel flow stabilizes.

Passengers didn’t particularly enjoy this indication system on the Navajo as they would get worried watching the fuel gauge dip to zero on the outboards long before the flight was over. Made them very nervous. I believe the Pressurized Navajo and Cheyenne had individual tank indicators, but I’m not sure.

In Navajo passenger service, you really wouldn’t want to run the tanks all the way dry before switching. Maybe switch with a minute amount of gas left in the tanks. The L/R fuel pressure or fuel flow (I can’t remember which) annunciator would go off, indicating fuel flow was getting weak from the almost empty tank and you had 5-8 seconds to switch. In reality it was more like 3 seconds. If you were distracted in hard IFR or had your hands somewhere else in the cockpit and missed the warning light, the engine would start bucking and surging like crazy until it either died momentarily or you switched to the proper tank. Not a problem in cargo, which I flew.

Hope this has been somewhat helpful. Good choice of airplane! I loved the Navajo (although I flew the larger Chieftain). I miss flying it, but greater opportunities came along in my career. Now I relive those days at home.

Hi! How are the Flight Dynamics of the FSX Navajo 310 compared to the real one that you flew??  

Are the Power plants well modeled in this model?  If those engines are Turbo charged why must lean on climb to keep the power up like an aspirated engine..  

Any other observation that you can share about the plane?  

Redgards 

RB 

Share this post


Link to post
Share on other sites

Let's see what I remember:

Flight model seems accurate (although I flew a 350). Feels heavy like the real airplane. Only thing missing is my left arm constantly hurting from having to force the airplane one-handed through takeoffs and landings.

Both models (350 and 310) are turbocharged and losing manifold pressure in the climb happens in the real world as well. You need to increase the throttle as you climb to maintain manifold pressure, not adjust the mixture. I take it you're climbing at full power? In the real airplane we'd reduce the manifold pressure to a climb setting at 1,000 feet. Otherwise you risk burning up the engines. We'd also set the mixture at 1,000 AGL to a certain fuel flow (18gph in the 350... don't know what to set in a 310... maybe 16gph would do) and leave it there until cruise, where we'd set it to a certain value of EGT. We adjusted the throttle as altitude increased because the engine wouldn't be able to maintain a desired manifold pressure due to reduced air density at higher altitudes. There's a very technical description I've included on how the system works a paragraph below this, but if you're interested in getting back to flying, I'll share a few power settings with you that'll work just fine in the sim (set the mixture as you like, but you only need to adjust it at 1,000, then again at cruise, don't touch those settings until you touch down):

Takeoff:                   Climb (>1,000 AGL)                         Cruise:
MAP: Full                 MAP: 38"                                           MAP: 30"
Prop: Max RPM       Prop: 2400 RPM                                Prop: 2300 RPM
Mixture: Rich            Mixture: 16-18 gph fuel flow              Mixture: EGT 75 Rich of Peak Temp or 1525, whichever less

Here's How the Turbocharger Works:
In the Navajo engine, the turbocharger is controlled by two controllers: 1) Differential Pressure Controller, and 2) Air Density Controller. The differential pressure controller controls the turbocharger wastegate (which controls the speed of the turbocharger) at low to medium power settings. It does this by maintaining a certain pressure in the area between the turbocharger and the throttle plate (known as "Upper Deck Pressure") that is greater than the pressure between the throttle plate and engine inlet (known as "Manifold Pressure" or MAP). The throttle plate provides a restriction that makes this differential pressure possible.

So, when you open the throttle, it moves the throttle plate to a more open position. That removes the restriction from the upper deck, which causes the differential pressure controller make up for the reduced pressure by speeding up the turbocharger to increase upper deck pressure until it is back to 6.0-6.5 inHg higher than the MAP. This works great until you go to full throttle.

At full throttle, the restriction from the throttle plate is gone, and it's impossible to maintain the higher upper deck pressure differential. At this point, the differential pressure controller could speed up the turbocharger so much that it can produce enough pressure to overboost and damage the engine. This is where the air density controller steps in.

The air density controller measures the actual density of the air exiting the turbocharger, and once the density reaches a certain value, it stops the turbocharger from going any faster, which allows the engine to produce only as much power as it can at a given altitude. This happens on takeoff, and to a certain extent climb. Of course, that's provided that you're at a high enough altitude to require full throttle to maintain your climb MAP setting. At this point, you won't be able to maintain a higher power setting. Perhaps you can adjust the mixture at this point, but I've never flown a Navajo high enough to need to so I wouldn't know much about that.

Hope that was somewhat helpful. Good flying!

  • Upvote 1

Share this post


Link to post
Share on other sites

Oh, and other things I've noticed... Hmmmmmmm. Well, the airplane in the sim certainly lands like a real Navajo: hard. The plane seems incapable of landing smooth, but that was perhaps my own fault. I've learned how to land a turbine airplane since and I'm pretty sure there would be a few things that I could transfer back to the Navajo should I ever fly one again. Other than that, I'm quite impressed with the fidelity of the modeled airplane to the real thing. I've re-flown a number of my old routes, and sometimes I swear I'm back flying cargo down the coastline and having to wing my way through and around weather at low altitude. Good (and sometimes scary) memories.

  • Upvote 1

Share this post


Link to post
Share on other sites
3 hours ago, StarvingPilot said:

Oh, and other things I've noticed... Hmmmmmmm. Well, the airplane in the sim certainly lands like a real Navajo: hard. The plane seems incapable of landing smooth, but that was perhaps my own fault. I've learned how to land a turbine airplane since and I'm pretty sure there would be a few things that I could transfer back to the Navajo should I ever fly one again. Other than that, I'm quite impressed with the fidelity of the modeled airplane to the real thing. I've re-flown a number of my old routes, and sometimes I swear I'm back flying cargo down the coastline and having to wing my way through and around weather at low altitude. Good (and sometimes scary) memories.

Wow thanks for all those experiences, you're right that's help a lot, 

One last thing, do you flew the Chieftain of Alabeo too? Can you say that fly like your cargo Chieftain?  

Redgards 

RB 

Share this post


Link to post
Share on other sites

 

4 hours ago, StarvingPilot said:

Oh, and other things I've noticed...

Hi Folks,

This kind of info is like gold in my book - thanks for sharing...

Also wondering - just what it would take to "fix" the fuel system - is it simply an XML edit - or - something we don't have access to ?

I think we got Alebeo to fix the fuel system on the C310 - thanks to Les...

Regards,
Scott

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now