Question to other Hawker Pilots

[g159av8tor]

I'm posing a question concerning minimum climb speed in the Hawker 800. We operate two XPs with API winglets and half of us pilots use the holding fuel flow chart (best endurance) to obtain minimum climb speeds per weight to cruise altitude fearing they will get too far back on the power curve. The other half us do not use this technique and use 180 KIAS as a minimum from other airplanes we've flown. Our Ops Specs don't address this issue.

Since there is no minimum published from Raytheon, Flight Safety instructors (Bob Dover, et al in ICT) reiterate that factoid.

Any guidance? Tailwinds...

 

[Roadie]

Min climb speeds

Is there some reason that you would want to climb at some "minimum climb speed"? The airplane does fine at 270kts/.70 in the climb. Why would you want to mush along at 180kts or whatever...?

I don't know about the winglet modded airplanes but in a standard XP, LRC at .70 will get you the max range out of the airplane. I don't think a slow climb would make any difference, if that's what you're trying to achieve.

 

[g159av8tor]

Is there some reason that you would want to climb at some "minimum climb speed"? The airplane does fine at 270kts/.70 in the climb. Why would you want to mush along at 180kts or whatever...?

I don't know about the winglet modded airplanes but in a standard XP, LRC at .70 will get you the max range out of the airplane. I don't think a slow climb would make any difference, if that's what you're trying to achieve.

My question is best described in this scenario:

I'm taking off at MGTOW at 32*C from FL going to CA. It's an ISA +15 day all the way up to FL410. Can I / should I stay on the M.63 climb schedule climbing nicely at a rate of 1200FPM all the way up (slowing to approximately 180 KIAS) or stop at 202 KIAS for the current GW (as shown in the holding chart) and take whatever climb rate she'll give me?

Tailwinds...

 

[HawkerF/O]

My question is best described in this scenario:

I'm taking off at MGTOW at 32*C from FL going to CA. It's an ISA +15 day all the way up to FL410. Can I / should I stay on the M.63 climb schedule climbing nicely at a rate of 1200FPM all the way up (slowing to approximately 180 KIAS) or stop at 202 KIAS for the current GW (as shown in the holding chart) and take whatever climb rate she'll give me?

Tailwinds...

You are going about it all wrong. Throw that .63 business out the window. You are too concerned about the rate of climb.

1st, Don't go directly to 410 for 2 reasons. It's just not going to do it and it's the wrong altitude for the direction of flight.

Your concern should be how you get to 400 which determines how fast the aircraft will accelerate, not how fast you climb. If you climb it at .63, the plane is just going to sit there and not accelerate when you get to altitude. Any fuel you thought you were saving by climbing at a high ROC will evaporate as the aircraft struggles to pick up speed. It's just that simple. You can be at your initial altitude in 25 minutes and 110NM from departure apt and the aircraft is sitting on its tail trying to accelerate, or you can be at your initial altitude in 32 minutes/150nm and on speed. Personally, I'd rather be on speed having burned a minimal amount more fuel which I'll get back once I'm at my final altitude.

Here's what you do. Climb the aircraft at 250Kias to 10,000. Above 10K, lower the nose and accelerate to 270-275 so you don't get the Ventral horn at 280. Climb the aircraft at that speed until it intersects with Mach .68 on the airspeed indicator. Once .68 is achieved, the plane should continue to pick up speed, so keep raising the nose in order to keep it at .68M. As long as you are getting 500FPM, don't worry about the ROC. You'll get better than 500, but the last 3 or 4 thousand you might be close to 500.

You are going to have to step climb it at this weight and temp, so level off at FL360 and let the aircraft accelerate to .70M, which is Long Range Cruise, or LRC. As the aircraft gets lighter, it will accelerate on its own, so if you want to make California, keep pulling it back to .70M. When the aircraft is light enough, climb it on up to FL400 and remember to keep it at .70M once you get up there. If it's not too busy (other traffic), tell the controller you want a slow climb, and climb it at 300 or 400 FPM. You'll keep your speed up by doing that and it wont take so long to get back on step once you get up top. They may or may not approve that, so worst case, climb it at .68.

Finally, use the PERF computer on the FMS. It's very accurate. I've only used the Honeywell, but if it's a ProLine 21 unit, the data will be just as accurate if not better. That will give you a good idea of how you are going to do and at what altitudes.

 

[g159av8tor]

You are going about it all wrong. Throw that .63 business out the window. You are too concerned about the rate of climb.

1st, Don't go directly to 410 for 2 reasons. It's just not going to do it and it's the wrong altitude for the direction of flight.

Your concern should be how you get to 400 which determines how fast the aircraft will accelerate, not how fast you climb. If you climb it at .63, the plane is just going to sit there and not accelerate when you get to altitude. Any fuel you thought you were saving by climbing at a high ROC will evaporate as the aircraft struggles to pick up speed. It's just that simple. You can be at your initial altitude in 25 minutes and 110NM from departure apt and the aircraft is sitting on its tail trying to accelerate, or you can be at your initial altitude in 32 minutes/150nm and on speed. Personally, I'd rather be on speed having burned a minimal amount more fuel which I'll get back once I'm at my final altitude.



Finally, use the PERF computer on the FMS. It's very accurate. I've only used the Honeywell, but if it's a ProLine 21 unit, the data will be just as accurate if not better. That will give you a good idea of how you are going to do and at what altitudes.

Thanks for the info.

With the API winglets, the 800XP2 accelerates nicely under hot and heavy conditions and will straight to FL400/410, 2000 to 4000 feet above the standard 800XP charts for max cruise altitude for temp and weight. The PERF landing fuel calcualtion is always 300-600 pounds lighter than actual reserve amounts, about a 100lbs per flight hour increase in reserve gas. The shorter the flight, the more accuarate it is. Less variables I guess. We've gone from having 0 reserve to 1500lbs during a transcon flight westbound as calculated by the ProLine cruising at M.75. For us, that speed gives us the best FF for the speed, usually 4-6 longer than MAX speed and up to 700lbs of fuel savings, depending on the length of the flight.

Again, thanks for the reply.

tailwinds....

 

[KSUPILOT]

250 to .70 / .70 to altitude! Never run out of speed or climb!

 

[Raskal]

250/.70...in the xp it never fails (at least until it gets hot and you go too high, the power still isn't that great, winglets or not)

 

[HawkerF/O]

Are you saying at MGTOW and +15 all the way up, the 850XP (winglets) will go straight to 410 without a step climb? If that is is case, WOW! Not your father's Hawker. That would open up a lot of places for the Hawker, mainly PHNL without the pucker factor or possibly having to turn around if the winds are stronger than 50-60 Knots on the nose.

As for the PERF calculations, are you entering the winds as well in the computer or are you just putting the FLxxx and cruise speed, letting it figure out the rest? I found that if you enter the winds (Duats or FLTPLAN), the #s work out really well. Try entering the winds at every fix, as +300-600lbs is quite a difference.

Something is not working/being programmed correctly if you are seeing 0 fuel at landing during the climb out. On FMSs without perf computers, you'll see that if you are going within 20-30% of the aircraft's endurance limit, or planning on landing with less than 25% of mission fuel: 1500lbs = 225 US Gallons. NON-Perfs use current fuel burns and speed only, then does the math, giving you your destination fuel, ETE, and ETA as if you were to continue at your current fuel burn and speed. As you climb thus becoming more efficient, especially once at altitude and on speed, the FMS will "create" fuel to give you a better and more accurate ETE, ETA, and idea of what you are going to have upon landing in terms of fuel.

On units with PERF computers, it takes into account things that non-Perf computers do not, such at 250 below 10, enroute winds (some), VNAV data, fuel burns based upon altitude and speeds down the road, etc, then computes all that data taking those factors into account and spits out a fairly accurate #, typically within 2-7 percent. It's good enough to calculate ref speeds/weights during any regime of flight without having to do the math in your head.

Also, I'm thinking the API winglets are aftermarket, so have you adjusted the default setting of your PERF computer to reflect the change in performance? For example, do you still need 1500lbs as a reserve, or can you plan for less? What are you telling it you are going to use for a climb schedule, cruise speed, and decent speed? To keep it simple, tell the FMS as much as you possibly can and the #s will be spot on. Try telling it winds at every fix, and winds and aircraft speed at every fix below 10. Don't forget the approach segment. Tell it at the FAF you'll be at whatever the plate says you should be at and REF+10 (if that is what you use). Create a fix at the Threshold, and tell it you'll be at REF and 50ft above it when you ge there.

Finally, if you typically cruise at 400 or 410, there is not a lot of traffic up there, so you're more likely to get Direct more often than you would if you were down with all the Airline traffic. Could that be where you are getting the fuel saings?

Thanks for the info.

With the API winglets, the 800XP2 accelerates nicely under hot and heavy conditions and will straight to FL400/410, 2000 to 4000 feet above the standard 800XP charts for max cruise altitude for temp and weight. The PERF landing fuel calcualtion is always 300-600 pounds lighter than actual reserve amounts, about a 100lbs per flight hour increase in reserve gas. The shorter the flight, the more accuarate it is. Less variables I guess. We've gone from having 0 reserve to 1500lbs during a transcon flight westbound as calculated by the ProLine cruising at M.75. For us, that speed gives us the best FF for the speed, usually 4-6 longer than MAX speed and up to 700lbs of fuel savings, depending on the length of the flight.

Again, thanks for the reply.

tailwinds....

 

[Bandit60]

I was going to chime in but HawkerFO said it all. And I might add he did a nice job.

 

[HawkerF/O]

I was going to chime in but HawkerFO said it all. And I might add he did a nice job.

Thanks. We all slip through the crakcs every now and then.

Also forgot to mention that the newer PERF equipped FMSs will even calculate landing REF #s before you depart for that field and post them automatically on the EFIS display.