Jump to content

Sign in to follow this  
Epikk

APU Fuel Logic...

Recommended Posts

Hello again PMDG team...I was wondering if the APU Fuel Logic was defenitely out of the 737NG Series??

Share this post


Link to post
Guest wee_davie_2612

If it is, PMDG, any chance of adding it back in?CheersDavid

Share this post


Link to post
Guest wee_davie_2612

Bump... Anyone got an answer?David

Share this post


Link to post
Guest ba747heavy

The APU system does not take fuel from the tanks. Someone from inside of PMDG will have to tell you there plans, or lack of, for fixing it, because I don't know.

Share this post


Link to post

Thanx for the reply Fred...I miss this feature sometimes...:)

Share this post


Link to post
Guest wee_davie_2612

Hey,I know it used to be there, it's written in the update and fixes file:

Share this post


Link to post

> There is slightly more of an issue than that so I am sure we>will not see this feature back in the 800-900, Lefteris can>comment more on the reasons.>Unfortunately... That's the way I feel it too : "APU" won't be back... Seemed like a really complicated issue.

Share this post


Link to post
Guest wee_davie_2612

Go get Lefteris on the blower :)As I said above, my knowledge of gauge programming would half fill a thimble. The most I've done is simple XML click sposts, a couple of switches and radio controls.Hell, if PSS can do it....(I don't feel one bit guilty saying that, 'Once bitten...' as the saying goes) CheersDavid

Share this post


Link to post

David....Don't believe every schematic you read (I've made that mistake too many times before ;-)). According to the Boeing 737NG Maintenance Manual, the APU can use fuel from any tank. However, if all the main tank fuel pumps are off, the APU will siphon fuel from the #1 tank.Cheeers.Ian.

Share this post


Link to post
Guest wee_davie_2612

>David....>Don't believe every schematic you read (I've made that mistake>too many times before ;-)). According to the Boeing 737NG>Maintenance Manual, the APU can use fuel from any tank.>However, if all the main tank fuel pumps are off, the>APU will siphon fuel from the #1 tank.>>Cheeers.>Ian.Hey Ian,The schematic above shows that it can use fuel from all tanks but only if the boost pumps are switched on and the cross feed is open. If the cross feed is closed and all the boost pumps are on, then a fuel imbalance between the main 1 and 2 tanks will still occur.I would like to see it reimplemented aswell. The whole idea of a aircraft like this is to go for realism, the APU having no effect on the fuel quantity isn't realistic.John, what were the problems faced in the early versions?? I only bought the NGs recently, after they were upgraded to v1.3.CheersDavid

Share this post


Link to post
Guest Ray CYYZ

If memory serves, the PMDG fuel system does time slicing, alternating between the fuel tanks, stealing from one then the other and back and forth. This was required to fix some problems with the engines cutting out back in a earlier release or so I remember Robert's explanation. This had something to do with the way FS handles multiple fuel tanks and the limitations imposed by FS on the aircraft developer (ie: you can only pull fuel from 1 tank at a time or something of the sort, and they for obvious reasons needed to attach one engine to each tank separately which FS wouldn't allow).Not really sure of the specifics, but thats what I remember.Ray

Share this post


Link to post
Guest wee_davie_2612

Hey Ray,That'd explain why the APU can't suck gas from only the right tank then (under the conditions outlined above). Interesting.I'd still like to hear from Lefteris to see if it was looked into again for the upgrade and if any headway was made.CheersDavid

Share this post


Link to post
Guest Ray CYYZ

Yep, would be interesting to know if the SDK helped them out.I think it would really matter with all the extra tanks/configurations on the BBJ/BBJ2, it would be nice to get those 2 extra little panels added to the 800/900 to be able to have the extra fuel tanks even if they never do a full BBJ/BBJ2 release as a separate product.Ray

Share this post


Link to post

Hi David>I would like to see it reimplemented aswell. The whole idea of>a aircraft like this is to go for realism, the APU having no>effect on the fuel quantity isn't realistic.Just as a sidenote here. Usually at bigger airports you have ground facilities for electricity. APU is used for AC while boarding and for starting the engines. The time the APU actually runs is roughly 15 minutes or so. Now, the APU has a fuel consumption of 225 to 280 pph depending on load, so the average fuel burn for the APU would be 63.15 lbs or 28.7 kg. Not to much considering the total fuel burn for a flight.To me this is not a big issue, but sure it would be neat to have, even if the impact on fuel is minimal.Cheers,Mats

Share this post


Link to post
Guest wee_davie_2612

Hey Mats,I don't doubt that it would hardly be noticed. Over here in the UK, however, many of the carriers are low cost carriers that have fast turn around times (30 Mins). These carriers often rely only on the APU during stop overs. Add to that, say, approx 10mins between starting the APU, taxiing to the gate (most do this so that the APU has plenty of time to stabalise, AOM recommends a min of 2mins before full load is applied)and shutting down the engines. Then add another 2-5 mins for cool down and shut down.So going with the figures you posted that's 45mins @ 250pph = 187lbs Granted that is still a drop in the ocean comparably, but more significant than 60lbs.It doesn't really bother me too much, I'd just like it to be added for the sake of realism :)CheersDavid

Share this post


Link to post

>>To me this is not a big issue, but sure it would be neat to>have, even if the impact on fuel is minimal.goto say im with mats on this one... with every thing else the way it is do i really need to list?! the fact the a few kgs of fuel havent dissapeared from the fuel tanks isnt going to cause me any problems.i Must say working for one of the bigger UK Carriers, in the department that produces the fuel figures for flights we never plan for apu burn, we all know how big the CAA are on saftey and im sure if this was a problem we would have to plan for this.Just a thought"Lairy"Liam Reynolds

Share this post


Link to post
Guest Matthew Murray

More fuel will be lost from the tanks when you over-rotate than from use of the APU on the ground lolSeriously, I can see this digress into a topic of when to use the APU again, but what if we, erm...loose one of those nice IDG's, and we have to crank the ol' APU Generator up to pick-up the load, fuel useage will be important then, especially on some of the longer tirps I like to fly??

[P CLASS=style1] Matthew Murray [/P][P][sPAN CLASS=style1]-|www.precisionmanuals.com|-[bR][/sPAN]

http://www.precisionmanuals.com/images/forum/supporter.jpg[/P]

Share this post


Link to post

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  
×
×
  • Create New...