Fuel Consumption In LearJet 45

:)Hello, All: Today was my first flight in FSX, after many years of flying in FS2004. :D

All went well...except for one, little, problem :confused:

I flew from my base airport of Denver, Intl (KDEN) to McCarran Intl (KLAS). Just a shorty, about one and a half hours.

So, you can imagine my surprise when I looked in my fuel tanks and realized that I had consumed 399 gallons. Yes, that's right!!:( Half my fuel was gone!!:mad:

What, the hey??:confused:

I like simulating flight charters in my Lear to anywhere in the U.S. and Canada. No more of that until I figure out why this thing is drinking fuel like a drunk in a free bar.:confused:

Any suggestions??

Flight level at cruise? Set to MACH instead of IAS? KDEN to KLAS probably bucking some good head winds.

Alos if you are taking off with full tanks, the extra weight of the fuel and thin air at KDEN may make your climb a bit fuel hoggy. Are you doing a proper step-climb flying level for a time burning some fuel before climbing again?

I'll give that flight a go with 1/2 tanks to see if I get the same results.

I just completed the flight KDEN to KLAS 1/2 tanks, a total of 448.1 Gallons. Cruise altitude of 30,000 feet with 34 knot headwinds. Landed at KLAS with 186.3 gallons total fuel on board. Used 261.8 Gallons for the flight.

That will include all of the taxiing at KDEN from GA parking to runway7.

Y'all got me curious! So I flew the Default Lear IFR @18,000 as instructed. My cruise speed was set at .65G or 390kph SOG. Average fuel burn was 670-680pph each engine at .65G cruise. (I started the flight with full tanks to try and do everything as standard as possible.)

Climb-out and descent were both at 1,200fpm. SOG Cruise after descent to 3,800' as instructed, was 250Kph actual.

I followed all the ATC instructions and landed on 25R. Then after landing, taxied to the gate. Upon arrival at the gate I had 3,960# remaining, according to the gauge. Or a net fuel burn of 1,640lbs., which is a not quite 25% fuel capacity burn. My estimate on the flight planner before takeoff was a burn of 1198#.

Considering the differences in ATC routing, traffic, etc. I think that's fairly close. And, as I usually do, I flew about as fast as possible at cruise without setting off the over-speed alarms. Had I flown closer to "conserve cruise" the 1198# would have probably been very close to actual. And that's very close to a 20% fuel burn for the trip. Did you have your flaps partially down?

I just completed the flight KDEN to KLAS 1/2 tanks, a total of 448.1 Gallons. Cruise altitude of 30,000 feet with 34 knot headwinds. Landed at KLAS with 186.3 gallons total fuel on board. Used 261.8 Gallons for the flight.

 

That will include all of the taxiing at KDEN from GA parking to runway7.

Mr Z, what was your cruise speed at 30K? I was wondering if I'm the only one who pushes the speed envelope?:rolleyes:

Mr Z, what was your cruise speed at 30K? I was wondering if I'm the only one who pushes the speed envelope?:rolleyes:

Warp factor 9! Actually .72MACH and about 408knots ground speed.

Zip,

If you wouldn't mind, could you elaborate on your step climb technique, as in how long you're flying level, and how much Altitude you're gaining for a given block of time?

Same goes for the Descent...

It's one thing that has sort of kept me from flying Jets more, just because I want to be doing it 'right'... :p

Thanks!

Alan :pilot:

Zip,

 

If you wouldn't mind, could you elaborate on your step climb technique, as in how long you're flying level, and how much Altitude you're gaining for a given block of time?

 

Same goes for the Descent...

 

It's one thing that has sort of kept me from flying Jets more, just because I want to be doing it 'right'... :p

 

Thanks!

 

Alan :pilot:

OK, although I rarely, rarely start a flight with absolutely full tanks and I always fly with IFR with ATC giving full instructions. Anywho, if I did do a flight starting off with full tanks (better known as "tanks a lot"), I would do the takeoff and maybe climb up to 6 or 8 thousand feet, level off make any turns, as needed, and continue on for about 10 to 15 minutes. I would then climb at a slower rate maybe 1000FPM up to my next altitude, say maybe 18-22 thousand feet and the level off to burn off some more fuel. Next climb would be to my cruise altitude, let's say FTL360 still using about 500-800FPM, slow but steady.

Big iron like the 747, A-380 and such, hold a lot of fuel and are very heavy so quick climbs to cruise altitude are probably not the best solution.

Basically it's climb some, fly level some, climb some, fly level....like walking up stairs.

Now on Descent, I will request at least an altitude of 20,000 feet when I get about 150-120 miles out from destination. A slow descent of about 12-14 hundred FPM. From there, I let ATC give the rest of the descent orders and prep for landing.

Warp factor 9! Actually .72MACH and about 408knots ground speed.

So an 18 knots SOG difference. Considering the extra 12,000' of elevation and the time to go up and down that 24,000', it's probably a draw.:cool: And I'm guessing you're right on the over-speed limit as well!;)

OK, although I rarely, rarely start a flight with absolutely full tanks and I always fly with IFR with ATC giving full instructions. Anywho, if I did do a flight starting off with full tanks (better known as "tanks a lot"), I would do the takeoff and maybe climb up to 6 or 8 thousand feet, level off make any turns, as needed, and continue on for about 10 to 15 minutes. I would then climb at a slower rate maybe 1000FPM up to my next altitude, say maybe 18-22 thousand feet and the level off to burn off some more fuel. Next climb would be to my cruise altitude, let's say FTL360 still using about 500-800FPM, slow but steady.

 

Big iron like the 747, A-380 and such, hold a lot of fuel and are very heavy so quick climbs to cruise altitude are probably not the best solution.

 

Basically it's climb some, fly level some, climb some, fly level....like walking up stairs.

 

Now on Descent, I will request at least an altitude of 20,000 feet when I get about 150-120 miles out from destination. A slow descent of about 12-14 hundred FPM. From there, I let ATC give the rest of the descent orders and prep for landing.

I agree, "TANKS A LOT" isn't at all a way to save fuel. In fact that is one thing the commercial industry tries to avoid if at all possible. (Tanking fuel cancels out all their petty luggage etc. fees when it comes to making a too huge profit!:mad:)

However if you're renting a plane, say from a flying club, tanks topped off to start and end is usually the expected arrangement. But then they usually charge you flight hours based the Hobbs meter too!:mad::mad::mad:

In this case I went with full tanks to make an accurate as possible re-creation of his flight. That's also why I flew the IFR flight at 18,000' cruise, as the flight planner suggested.

Zip & Rupert,

Thanks for the Tips; I was looking at the whole thing from a 'general Procedures' standpoint. Before, I was never sure whether climbing straight to cruise or the step climb was the best way to go, especially with the big iron. And, I always seemed to always be too high, too fast and too close whenever I was prepping for Landing.

This gives me a much better foundation on which I can start out on, and go from there.

The aforementioned Flight sounds like a good one to practice with; I live in Denver, but usually fly out of Centennial (KAPA), which is only a few miles away.

Thanks again!

Alan :pilot:

A few thoughts.

There should be no reason to step climb the LJ45, it can climb straight to FL430 at MTOW.

Any time spent cruising down low will burn extra fuel as these planes are less efficient at lower altitudes.

The FSX flight planner offered 18,000 ft because that was the minimum enroute altitude for that path. Did you plan for the high level jetways?

Climbing at 1200 FPM down low in the Lear is wasting it's potential, 3000 FPM is more like it. The faster you get to altitude, the faster your engines will burn more efficiently.

Also, the higher you fly the longer your descent, where you can throttle back and let the plane glide.

Here is an example of an LJ75 that flew from KDEN to KLAS, study it's profile- http://flightaware.com/live/flight/LXJ471/history/20160627/2225Z/KDEN/KLAS

Only carry as much fuel as you need. Plan for 1000 lbs and 100nm for climb, 1000 lbs for each hour of cruise, 500lbs and 100nm for descent if you cruise ~FL410. This should get you close, obviously YMMV depending on payload, winds, etc.

peace,

the Bean

Mr Zippy: My cruise was at FL260. .73 Mach (A mistake, maybe? Maybe FL240 @ 280kts IAS would have been better

I took off with full tanks. A step-climb? Well, I followed ATC Vectors...14,000ft, FL220, FL260...:confused:

Mr Zippy: My cruise was at FL260. .73 Mach (A mistake, maybe? Maybe FL240 @ 280kts IAS would have been better

 

I took off with full tanks. A step-climb? Well, I followed ATC Vectors...14,000ft, FL220, FL260...:confused:

I also followed ATC in regards to turns and climbs. I was just answering ViperPilot2's question about step climbing with "Big Iron" and full tanks. My tanks at 1/2 full plus my extra height and MACH .72 maybe gave me the edge in fuel economy?

Just reflew the flight myself with 2,200# or about 1/3 tanks to start. I climbed as directly to FL430 at 3,000fpm as ATC stepping allowed. Then stepped down as instructed by ATC as well. Time for both flights was 1.6 hours each. Fuel consumption was down 480# for the flight. Low fuel lights on side tanks came on about 25 miles out, but landed and taxied fine.

RW IFR minimum fuel standards for this flight would probably call for about half tanks to provide for a safe diversion if needed.

I flew the route profile pretty much as depicted in the link I posted earlier (DEN-LAS).

With the default load of two-170lb pilots + four-170lb SLF + 150lb baggage + ~2600lb fuel at engine start.

Direct climb to FL430, cruise @ m.78 burning 720 lb/hr and a direct descent to the runway.

I had ~1200lb fuel at engine shutdown, so I burned ~1400lb.

FSX claims max range as 2200nm, this flight is about 600nm.

That means I flew more than 25% of the max range on less than 25% of the fuel.

If anything, this plane needs to burn more fuel, not less.

Of course, that range value is suspect.

All in all, it's close enough for the girls I go out with.

Can I suggest to you all the usage of http://flightaware.com/

You can browse flight tracking by aircraft type and find a profile similar to what you want to fly.

Or you can search for flights between two airports.

This is primarily USA-based, I just searched for all airborne LJ45 flights and found six returns.

This site is a great resource for seeing how real world ops work and registering is free.

peace,

the Bean

I flew the route profile pretty much as depicted in the link I posted earlier (DEN-LAS).

 

With the default load of two-170lb pilots + four-170lb SLF + 150lb baggage + ~2600lb fuel at engine start.

 

Direct climb to FL430, cruise @ m.78 burning 720 lb/hr and a direct descent to the runway.

 

I had ~1200lb fuel at engine shutdown, so I burned ~1400lb.

 

FSX claims max range as 2200nm, this flight is about 600nm.

 

That means I flew more than 25% of the max range on less than 25% of the fuel.

 

If anything, this plane needs to burn more fuel, not less.

 

Of course, that range value is suspect.

 

All in all, it's close enough for the girls I go out with.

 

Can I suggest to you all the usage of http://flightaware.com/

 

You can browse flight tracking by aircraft type and find a profile similar to what you want to fly.

 

Or you can search for flights between two airports.

 

This is primarily USA-based, I just searched for all airborne LJ45 flights and found six returns.

 

This site is a great resource for seeing how real world ops work and registering is free.

 

peace,

the Bean

Thanks for the "heads up" on FlightAware Mr. Bean. I just went there and signed up myself.;)

Bean,

You wrote...

"Only carry as much fuel as you need. Plan for 1000 lbs and 100nm for climb, 1000 lbs for each hour of cruise, 500lbs and 100nm for descent if you cruise ~FL410. This should get you close, obviously YMMV depending on payload, winds, etc."

Is this a good set of General Rules for all Jets, or just the Lear?

Thanks to everyone for posting their Tips; personally, it's going to help me out quite a bit as I try and figure these birds out!

Alan :pilot:

Is this a good set of General Rules for all Jets, or just the Lear?

Those were specific to the Lear, each plane will be different.

They are also a little heavy to provide for reserves.

The best thing to do in the sim would be to make a few flights and keep some detailed records about fuel burn.

Keep track of how much you burn climbing to cruise, what your burn rate is in cruise and how much you burn on descent.

Also take a look at how far you fly to get to cruise and use the "rule of three" to calculate TOD. You can then subtract that mileage from your total to calculate fuel burn at cruise.

I like to figure my fuel burn, add a reserve and then fly the flight to see how close I was.

Another "something" to make the sim both more interesting and more realistic.

peace,

the Bean

From everything I've ever read, Lears are known for their performance.

So I always fly mine like they're stolen. ;)

250 KIAS up to 10K and then kick her in the tail up to cruising alt. The aircraft almost seems to be champing at the bit and saying to me, "What you waiting for, chicken? Turn me loose and let me show you how a REAL bizjet flies!" :D

From everything I've ever read, Lears are known for their performance.

So I always fly mine like they're stolen. ;)

250 KIAS up to 10K and then kick her in the tail up to cruising alt. The aircraft almost seems to be champing at the bit and saying to me, "What you waiting for, chicken? Turn me loose and let me show you how a REAL bizjet flies!" :D

That's an apt description!:cool::cool:

That's an apt description!:cool::cool:

Thanks! :D

As an aside, back from 2000-2002 I used to work in an office about 300 yds East of the end of Rwy 15 at KADS (which is also my virtual "home" field and one of the busiest "executive" airfields in the country).

There are several Lear 25s that operate from that field (plus a B732 Shorty, plus the A/C from Cavanaugh Flight Museum).

When those -25s or the Shorty would spool up prior to T/O, the entire building vibrated! :cool:

I always tried to make it a point to head out and watch 'em roll. As soon as I opened the front door, the Big Boss would be like "#^#$@## Matt!" ('cause that's my name). ;)