Fuel saving techniques Hawker800XP

[Captain Smiley]

Hi all,

Does anyone have any recommended techniques for saving fuel on Hawker 800XP.

We are very happy with ours but would like to cut down on our fuel bill.

We normally climb at about 280kts, cruise about M.76 and descend at vmo

[supermoix]

IMHO not much, I tried for several years and basically no other climb, descent profile will save fuel in the Hawkers.

The only things we could do to save some fuel was to:

- Step climb to optimum all the time (with ATC help)
- Slow down to mach . 72-74 in cruise.
- Reduce your fuel load for a lower TOW will help a lot to get you higher soon.

But those above are obvious of course. but no tricks that i could find.

[Denim and leather]

Hello,

Try 250kt as climb speed,and M0,70 if you are not to much hurry.
Safe flights:ok:

If you need help you can pm.

[Flintstone]

What does the manual say?

[Denim and leather]

That's the manual say.

Safe flights:ok:

[Habari]

Climb at 250kts to Mach 0.63. Maintain 0.63 to cruise altitude and then use manual for long range cruise settings.
No other secrets, manual knows best.

[B200Drvr]

Or 250 kts to .70 which is the "normal climb" in the book. .63 is the best rate of climb and then use the book for long range cruise settings. As was said above, "the book knows best".

[Captain Smiley]

Thanks all. Any other tips on the 800XP appreciated.

[natops]

Hi there smiley,

If you enter the aircraft via the main entrance, the cockpit is to the left!:}




Yes yes I know, but I couldn't resist OK!

N.:ok:

P.S. A real one: if you cant dim the reading lights above your head, try the rocker switch behind the FO seat. That one caught me once. Same reading lights will be on when you swith on the entrance light, but when the rocker switch is in the up-position they will not extingish, and will not be dimmable when you switch off the entrance lights.

[Miles Magister]

Smiley,

It may be stating the obvious but with all the talk above about varying the cruise speed do not forget your support+ payments. If you reduce your criuse speed then your flight hours and consequently your support+ payments will increase.

forgive me if you already have this calculated.

Regards

MM

[TKS850]

Have any Collins Pro Line drivers had any experience with an "Unable cruise alt" msg on their FMS.

I can't seem to make sense of the Flight Manual, Weight V's Height tables compared to what the FMS is saying.

Is the Buffet boundary chart considered by the FMS.

Any ideas appreciated.

[Phil77]

If you reduce your criuse speed then your flight hours and consequently your support+ payments will increase.


Assuming 40.000 ft:
Mach 0.76 = 501 mph
Mach 0.70 = 462 mph
Difference = 39 mph

2 hours at cruise: about 10 min slower

I don't have the DOC's for a 850xp, but used the above calculations on other light and heavy aircraft (Beechjet 400a and Falcon 900B) to get the extremes:

You need to achieve in excess of 125-180 pounds per hour less fuel burn at Mach .70 than at .76 to compensate for the higher operating cost.

(Falcon 900B: 180 pph; Beechjet 400a: 125 pph - I was using $65 Labor rate, actual MX plan costs)

Disclaimer: certainly there is room for error - running for cover

...yes, I was bored. :8

[Miles Magister]

TKS,

This message appears in all PL21 aircraft frome the Hawker to Citations to King Airs and can be at medium levels as well as high levels. Could it be the flight planned route entered has a leg on the wrong semi-circular or a leg which is not allowed at that height in that direcection on that airway?

MM

[medriver2008]

I have a pop quiz for the hawker operators.

You select gear down and it sounds like it is down and locked but you have no main gear indication on the back up lights.

In other words, prove the gear is down and locked by using the horn warning system.

name 4 configurations you can have that will confirm to you by the warning horn system that the gear is down and locked?

[natops]

aeroncaman is correct, if you change cruise level on the perf init page to a lower altitude where you can reach the cruise speed inserted on the vnav page/cruise then the message will disappear.
Of course you can change the cruise speed to a lower setting as well.

The message does not mean that you cant safely fly at the altitude put in the perf init page, but you will probably not reach the speed as selected on the vnav page/cruise.

N:ok:

[Seaeagle109]

medriver2008,

I can think of three to use while airbourne to confirm the gear is down and locked.

1/ Power above 60-70% N1 with the airbrakes extended(obviously use flap 0 to check this one), horn wll sound with gear down & locked

2/ Power below 60-70% N1 and airspeed below 150kts(watch the AoA if you don't have the flaps out), horn will sound without gear down & locked

3/ Flaps extended to 25 or 45 degrees, horn will sound without gear down & locked

Another for on the ground

4/ Start power switch selected "on" with gear down and locked but gear lever selected up

Seaeagle109

" A man's character is his fate" Heraclitus(Old Greek guy)

[hawker750]

Fuel Savings on Hawkers:
1/ If you are using long range/ventral fuel tank, leave it in there for as long as possible to get aft C og G. Saves fuel

2/ The trim inputs from the A/P are not great. Ensure that the trim indecese are 100% flush by manually trimming if necessary.

3/ In the cruise select your mach number and let speed settle, then pull back throttles inch by inch untill speed just starts to decay. Careful use of this technique can save 50-70 lbs/hr with no speed loss!

4/ Do not tanker unless fuel price more than 5%/ hour of flight cheaper

5/ Buy fuel from World Fuel Service at Gatwick to save $$$$$

Have got 7 hours airborne from our 800 and landed with 1000 lbs using above techniques.

Happy long range flying!

[Dumbledor]

Hawker 750 said:

'1/ If you are using long range/ventral fuel tank, leave it in there for as long as possible to get aft C og G. Saves fuel'

The problem with this is if you delay the transfer, and you then have a problem with transfering fuel you will be at even more aft CG than you would if you did it after making just enough space for the ventral fuel in the wings. I flew with some one who did this on a ferry flight. When he went to the loo I had a big control problem (Aft CG). I started transferiing immediately and all was ok after that.

If the transfer doesn't work it is a diversion issue before it gets too aft loaded. Moving pax and baggage is then necessary.

On the original point, unless you trying to stretch out the range of the a/c, reducing flight time must be the priority. I depends how much you pay for the fuel but saving time on the a/c was always the priority on a bizjet. Saving fuel was more a priority for the airlines. DOC's are different because they are utilised far more.

If you can fly at FL400 with a similar TAS at FL380 (reduced headwind may help too) then you can save fuel without adding time.

On a stretched out 6hr trip at long range cruise, you can save around 30min of flight time if you can techstop halfway and cruise at high speed. (15-20 min on the ground of course). 30min must be worth around £600? We don't like arriving on fumes anyway unless all options are open, so stretching it out can be stressfull.

Climb at 250/0.7 and descend late ie set VNAV to 3000fpm is good for long range.

[G-SPOTs Lost]

Climb at 250/0.7 and descend late ie set VNAV to 3000fpm is good for long range.

Thats good for most types, for those able to set FPA (honeywell?) then 3.7deg will give you around the same descent point as your typical boeing/airbus profile now that fuel price has come down again.

descending at the same rate and point as the airliners saves fuel and prevents vectoring/time. Good one for this is AGP 3.7deg means thust levers closed at around 95-100miles/F410 and not touched again until the FAF! - good for 250-300lbs on my aircraft not hawker but similar mid size

[Dumbledor]

Thanks for that, GS. It's interesting to hear what the bus drivers do. Most of us use 3* ht, ie from FL400, 120nm, around 3 deg. 3.7deg is around 2.5*ht, so from FL400, 100nm. Sounds good.

[KERDUNKER]

On the Bus you go down when the box says so.. remembering of course crap in leads to embarassment, high speed (in an effort to get the height off) and a go around burning more fuel because you forgot that she is reluctant to slow down! Go down slow down she wont do!

For fuel calcs/saving, actual (at your level) TAT/SAT in the computer makes a massive difference and if blessed with auto thrust then in cruise go to manual as once set power will be constant thus saving fuel over A/T (A/T constantly changes thrust to maintain managed/selected speed)

[hung start]

250 into .70 then LRC by the book got us 6hrs 40 with 1300 pounds on arrival in an 800xp (honeywell). Just picked up a 900xp and getting the unable crz , now i know how to fix it thanks . We have decided that it is cheaper to fly max cruise , less time on the MR , less MSP, Less maitenance and at resale less hrs .We have also found that climbing at 280 into .74 at isa +10 and high t/o weight we are getting better climb rates in the high 30,s upto 410 then we accelerate much quicker . We only have 40 hrs on the 900 but so far this seems to work .I am open to other suggestions . Just for the record it performs much better than the 800 ,and better than book figures in cruise . Sounds a bit like a salesman but im not .

[hawkerjet]

As someone attested to in a previous post, be careful about leaving fuel in the Ventral Tank too long. I just double checked my 900XP AFM and it's not an option for us. It states we "shall" transfer fuel from the ventral to the wings when each wing has 3300#s. In the case of fuel not transfering from the ventral, well you can continue the flight so as to land not more than 22,500#s. Seeing that the average weight of a 900XP is around 16,500, that doesn't give you a lot of time to get on the ground.
Be careful.
Does anyone turn both MAV's to LP ON at high altitude and longe range. I have heard about this in the older hawkers but haven't wrapped my head around the systems yet....:}

[maxphlyer]

Yes, the good old Viper engines...

The vipers were simply not strong enough to handle the bleeds at all times.

One of the historic remains of the Viper era is the step in the descent checklist: "main air valves - on".

On the Honeywells there are 2 ports to feed the pressure system, a high and a low pressure port. Normally the LP port is sufficient to feed the system, but at low RPM the HP port might be needed, if the LP pressure is not high enough. With the main air valve switch in the "ON" position the switchover from LP to HP is handeled automatically. With the switch position "LP" the system is forced to stay on the LP port.

The Honeywells will put out enough power and pressure in cruise, so the bleed system will stay all the times anyway on the LP port, unless you reduce power for the descent. Switching it to "LP" does not improve efficiency.

[hawker750]

Why would fuel not tranfer? I have never heard this ever being a remote possibility on the 800 series as the cock is mechanically conected and the transfer is via jet pump. Is it different on the 900? As long as the C og G stays in the envelope I see no problem.

Another question? On the 750 series the long range fuel tank is substituted for a baggage bay. Do you have to transfer the bags to the cabin when the fuel gets to 3300 lbs in each wing. Could be quite a tricky operation for the co-pilot!!

[Dumbledor]

The ventral on an 800xp holds 1650lb of fuel as I remember and is either full or empty. Pax baggage is not normally that heavy. Fuel is transferred by jetpumps powered by the wing fuel pumps. The ventral tank lever could be stuck due to cabling, valves etc. A blockage or airlock could also trap the fuel. It's best to transfer at 3300lb a side or whatever the good book says. It's not worth delaying it or you could enter test pilot terretory.

[natops]

H750,

to answer your question:

The copilot only has to transfer the bags when you have filled the EBC with 1500lbs of luggage. (which is of course not allowed):eek:

N.:ok:

[hawker750]

The next question for you 850/750 experts.

On the 800/850 the weight of the fuel in the long range tank is not a zero fuel weight item. I.E. you load up the cabin up to your max ZFW then load max wing fuel and then load full fuel in the long range tank. (subject to Max gross)
On the 750 does the baggage weight in the external baggage bay get added into the zero fuel weight or is it added in afterwards as in the 800/850?
I suspect that the weight in the extenal baggage bay gets included in the ZFW. If that is the case how does the airplane know whether it's fuel or baggage down the back?
Perhaps somebody who has done the 750 course could answer.

[Dumbledor]

Sorry H750, i've not done a 750 course but have flown an -800 without ventral a few times.

The ventral fuel tank is supposed to be empty on landing, so the vental fuel is not included in the stress calc's for landing. You are limited to 280kt with ventral fuel. I'm not sure why but it could be to do with reducing wing bending moments for the design upgust calc's.

On a LJ35 which has a fuselage tank. You can land with fuel in it but there is a Max Wing Bending Wt which is the include ZFW + Fus tank fuel.

(By the way, I was told that if you had to land immediately after T/O with full fuel, you could jettison the ventral fuel by using AUX TFR. it would come out of the wing tips. This is not in the manual. I would only do this if the RW was too short for an immediate overweight landing.)

[apruneuk]

I believe that the reason the ventral tank has to be full or empty for take off or landing is due to the fact that it has no internal baffling, unlike the wing tanks which are divided into sections. The possible outcome was demonstrated a few years back when a certain sea ferry set off with its bow doors open and subsequently rolled over when the water it ingested started sloshing around inside.

[formulaben]

A question for the Hawker experts here: based on your experience, what is the best method for loading passenger baggage? Which method do you use? Anything other than these?

1) let pax bring their own bag onboard and self-stow
2) have other pilot grab bags and load prior to boarding
3) have pax bring bags to airstair, and pilot loads after pax boarding

Any info appreciated.

[Max Payne]

3.

1 is the Ryanair technique.

[B200Drvr]

Guys, You dont need to fiddle the the defaults page to get rid of this. It is there to tell you that with the ISA you have put in, at the weight you have put in, that the aeroplane cannot make that Alt. Use it like it was designed, update the ISA on the perf init page as you climb, to see what the optimum altitude is for that weight. I use it on every flight, it works great.
Another tip, which very few people seem to use. Make sure all your defaults are correct, PM me if you cant find them, Set your vert and lateral nav for take off as Hdg - VPitch, after gear up, hit FLC go to the FMS hit PERF x 2 (perf menu) and hit resume. This will give you your climb all the way to cruise, and will honor any altitude restrictions on sids or airspace. Very important to ensure that the vnav defaults are correct.

[Scroll Lock]

Hawker 750....

Surely you are joking right ??

Q..When DO YOU HAVE TO transfer fuel from ventral to mains ?
A.. at 3300lbs. ONLY at 3300lbs, not before, or after.

Please re-read your AFM, mate
:ok: