MD-XX Fuel planning - Can you please help?

[thrillsandchills]

Here's the thing: the online "handbook" says at 31 thousand feet, fuel burn was (for the MD-83 - the section of the manual I was looking at,) 3.14 kg X 10.

Would somebody please provide me with a) an explanation of what the above expression means and b) how to convert it into pounds, so that I can do fuel planning.

Just out of curiosity: why are these fuel flows in KG's when (correct me if I'm wrong,) all the rest of the fuel flows (in all the other online "handbooks") are in pounds?

Thanks in advance,

Thrills And Chills

 

[christrott]

The manuals and charts are available in both LBS and KG depending on the operator's configuration. There's actually quite a few aircraft operating here in the US with US registrations and operators who purchased the aircraft from abroad and chose not to spend the money to convert them from KG to LBS.

As for the fuel flow, 3.14 x 10 = 314kg/hr. Then just do a straight conversion from KGS -> LBS by taking the KG and multiplying by 2.2 and you'll get close if you don't want to use an online converter.

[aerofoto - HJG Admin]

why are these fuel flows in KG's when (correct me if I'm wrong,) all the rest of the fuel flows (in all the other online "handbooks") are in pounds?

The panel I used to test each of these simulations was the SOUTHEY B717-200/MD-80/-90 glass panel version .... which reads F/F in terms of "K" values

The glass type F/F gauge face indication read F/F per units of "10K" .... so .... that's what I endeavoured to quote .... only somehow the "K" portion of this indication got left out and a "KG" reference was eroneously inserted .... both "typos" .... which I'll correct when I've time to do so since there's a lot of entries that'll being individually adjusted.

PERSONALLY ....

I'd interpret "10K" to mean 1000 .... meaning .... if the guide states "3.14" (which it did at the particular altitude and velocity quoted .... and using that particular panel version also), then, multiply that figure by "1000" .... and the said value should theb be translated to read "3140" .... suggesting a F/F indication of some 3,140 LbS per hour.

It should also be noted that the Flying Guides do clearly state the panel version used with each simulation being "SOUTHEY" .... meaning .... the said SOUTHEY B717-200/MD-80/-90 glass panel version.

Using another/any other of the MD-80 panels versions offered by HJG, or elsewhere, will likely result in entirely different F/F indicications .... simply because the F/F gauge callibrations, and by implicatition their indications, will obviously vary .... and possibly qiute considerably too.

It also needs to be born-in-mind .... that whilst each of the 4 MD-80/90 panels offered by HJG work perfectly with each of the MD-80/-90 simulatios we offer .... neither has, yet, been "custiomised" to the standard we'd like .... unlike is the case with most of our other panels, so, I'd recommend treating the like of the F/F indications in these panels "with a grain of salt" .... in that whatever's displayed is "an indication" (obviously), but, not necessarily an accurate/authentic one.

Masrk C
AKL/NZ

[thrillsandchills]

Ok, Thanks for the clarification.

Then the question becomes, (in my mind anyway,) How accurate is the FDE when compared to the actual "real life" aircraft? The reason I ask is, I did a search about fuel flow specifically about the MD-83. The web page gave the answer of between 2800 and 3000 lbs per hour. Granted they weren't referring to the a simulation, but that's the "real life" figure they came up with. I presume from the posters personal experience from flying the MD-83.

Thanks in advance,

Thrills and Chills

[aerofoto - HJG Admin]

How accurate is the FDE when compared to the actual "real life" aircraft?

Don't ever confuse FDE with gauge programming/calibrations .... and which is the mistake I think you're in danger of making here.

Whilst there "IS", often, a relationship between the two .... both are actually separate.

Our FDE's (generally) are "as accurate was we can make them" .... given our current skill and knowledge base, BUT, bear-in-mind that FS is just FS .... "A GAME" .... at its very best !!!!

It "IS NOT" real world .... and "CANNOT" be real world .... by virtue of the fact it "CANNOT/DOES NOT" replicate the real world environments with total authenticity .... mostly because it doesn't feature sufficient parameters that can be manipulated in order to be able to arrive at more accurate conclusions.

Real world aviation is subject to a variety of both scientific and phisics based dictates .... which the game, whilst it may be fun, for some, simply cannot be reflective of everything else.

If it did .... then fewer people would pobably be able to use it well.

What I'm saying here (trying to at least) is ....

FS in based on a lot of BULLnuts & JELLYBEANS calculations .... "compromises" in other words .... and in order to be able arrive at the most convinincing conclusions possible, but, it's far from reality .... really.

I did a search about fuel flow specifically about the MD-83. The web page gave the answer of between 2800 and 3000 lbs per hour

.... and which is "pretty close" to the figure quoted within my last reply .... but .... for any avergage F/F figure quoted there's also a lot day-to-day, and environment-to-environment, as well as situation-to-situation conditions/influences that can, and do, ultimately impact actual/real world F/F indications in the field .... and by necessity fuel planning also.

Within FS .... a number of parameters are manipulable in order to be able arrive at a result that's often "close to" a known F/F indication, BUT, within FS also, the best we can usually ever hope achieve is to start out with a fairly accurate F/F "guage indication" at SL .... then .... through a series of influences we're forced to "have to" accept whatever F/F rates become by the time any simulation reaches virtual cruising altitude. Only these indicatios might, by this stage, be progressively out .... and like/accept it oerr not "THAT" is about as real as it gets

Mark C
AKL/NZ

[thrillsandchills]

I hope I didn't offend you by something I said in my post re: fuel planning. If I did, I apologize.

Since it wouldn't be responsible of me to use the 3140LBS (because they were derived from a different panel...

At this point, knowing what you know (about this thread,) how would you suggest I proceed? Where can I get my F/F numbers from?

Thanks in advance,

Thrills and Chills

[aerofoto - HJG Admin]

Why would I be offended ?

There's "absolutely nothing" within this (or any other thread) that I could possibly take offence to .... BUT .... I'll let any offenders know (in the future) if they ever do cross the line .... I assure you/everyone

Since it wouldn't be responsible of me to use the 3140LBS (because they were derived from a different panel ....
.... how would you suggest I proceed? Where can I get my F/F numbers from?

WELL .... I "tested" each of these MD-80/90 simulations using the panel version I've stated .... that being the SOUTHEY B717-200/MD-80/-80 glass version only .... and which "IS NOT" out of place among the early MD-80 series either .... because some of these aircraft were, apparently, upgraded to this (or a similar) instrument standard .... or so I'm told, but, since these simulations were first released by us, I've also now flown each of the other panel versions sufficiently, over the years, to know they all work equally well too.

"IF" .... you want to determine accurate F/F using either of the other MD-80/-90 panel versions, then, you're going to have to take yourself on "a voyage of discovery" .... and fly these up to virtual cruising altitude (you can still use the flying guides for these .... since the recorded data will/should be just as appliable) and note the F/F indications after you get there .... THEN .... you'll be able to use that information to determine your fuel requirements in relation to virtual flight planning later.

That's precisely what I've had to do in order to be able write the guides I try to provide .... certainly no Rocket Science involved with doing so

Why don't you just "ACCEPT" the F/F figures currently quoted for each MD80/-90 version .... then convert these these by a value of 1,000 to give you an approxumate hourly F/F value in LBS .... and be "CONTENT" with that ?

Regardless of the panel version you're intending to use .... although the indicated F/F might vary, due to the limitations of gauge callibrations, these indications aren't going to differ majorly from what's already been recorded .... maybe just show the engines drinking around a couple hundred LBS more, or less, in terms of any difference/s .... HELL myself, and the other modellers, all drank more than that last night at the model function we all attended.

In the case of a "non-customised" panel .... as I've previously stated each of our MD-80/-90 panel versions are .... don't get too serious with stuff like F/F etc .... "is all I'm saying".

And the guides proovided are .... "JUST GUIDES ONLY"

Mark C
aKL/NZ

[Mike Monce - HJG]

I hope Mark doesn't mind if I chime in here.. When we are working on the FDE's for these planes I check the fuel flow by comparing the model's FF to the actual engine data:

www.jet-engine.net/civtfspec.html

The first column on that great web site gives the thrust for the engine, the second gives the SFC, which is the fuel consumption at sea level and 100%N1. Basically multiply the thrust by the SFC to get the FF. I then compare the FF at sea level in the model to the real world data. Then the fuel flow scalar in the cfg file can be adjusted to get the proper result.

HOWEVER what happens after that, as Mark states, is a complicated interaction of the calibration of the fuel flow gauge in the xml coding and also a fuel flow curve in the air file. Bottom line: by doing that initial test at sea level we generally get the FF in the real world ball park; but probably not quite on "home plate"

Mike

[aerofoto - HJG Admin]

YEP .... that's the story .... and no problem at all Mike

We start off at ground level/SL with a computation that resuklts in a fairly accurate F/F indication.

Then .... subject to what happens within FS on the way up we can also influence these indications (+ or =) per nmanipulation of certain drag related parameters .... BUT .... ultimately have to accept whatever these figures are demonstrated to be by the time any simulation gets to cruising altitude.

The accuracy of the gauge calibratios is going to have the final say .... because it's by these that we read what's finally presented at any stage.

As I've hinted a couple of times already within this particular thread .... the MD-80/-90 panels we offer have not, yet, been customized to our favour .... and may never be since it's an extraordinarily time consuming process. Their gauges are OK .... but .... of a much earlier FS standard .... and I thinks it's (honest) not a put-down to say these not as accurate as those within our "customised" panels.

Other than that ..... what we offer is a very good and workable panel series with any of these MD-80/-90 simulations .... and that's why these versions (only) are offered by us.

One of many things I like about the panels which George has compiled/recompiled and othewise "CUSTOMISED" for us is that their/"HIS OWN" gauge programing is usually "very accurate"

Mark C
AKL/NZ

[thrillsandchills]

So, then - Just to make sure I've got this right - the fuel planning would be something like this: 3140 x2 which would be 6280 LBS to run both engines for for 1 hour...Right? (MD-83 @ cruise altitude of 31,000 used in this example.)

Thanks in advance,

Thrills and Chills

[aerofoto - HJG Admin]

If I was doing this then I'd plan along the following lines ....

3,140 LBS per engine per hour = 6,280 LBS covering the hourly fuel burn for both engines.

I'd them add 30 minutes "reserve" .... or half of the above indicated quantity again = another 3,140 LBS for a new total of 9,420 LBS.

And I'd' then add another 10% on top of that too .... or some 943 LBS for a final fuel loading of some 10,362 LBS.

That'll be quite sufficent to get anywhere one wants to go (in FS) that's within an hours flying time/range .... with a safety reserve of 30 minutes only .... and with the added assurance one won't be landing overweight or risking everything suddenly running "quiet" en route !!!!

Our MD-83's feature a 3-tank configuration .... so .... I'd distribute the above final fuel tally "evenly" across all 3X tanks .... and which would then result in a loading of some 3,454 LBS "per tank" .... to calculate all of this "quite crudely".

In reality though .... one should probably distribute the fuel loading across all tanks represented within any simulation insuch a manner that encourages the COG indication (within the MSFS PAYLOAD & FUEL PLAN) to move (if it will move at all) as close to the indicated wing LE as possible .... and which might mean reducing, or even increasing, the Center Fuel Tank quantity (only) somewhat in order to ensure this .... with a little juggling between Left an Right Tanks also.

That's how I'd do it .... and do in fact do it

Just make sure you don't end up with a fuel imabalance situation.

Mark C
AKL/NZ

[thrillsandchills]

Thanks for the confirmation and the additional information. I'm surprised you have enough fuel for ground ops and climbs and descents, etc, etc, not having specifically allocated fuel for it. I know you've been using this formula for a long time now, and it's never let you down.

Thrills and Chills

Thank you for mentioning about maintaining equally weighted. I always make a point of keeping the tanks of equal or as equally weighted as I can. (As far as I know): And that is why fuel is measured in pounds or kilograms, rather than gallons or liters; for weight distribution.

[aerofoto - HJG Admin]

For "FS purposes" (only) .... the above formula is fine.

Mark C
AKL/NZ