setting climb power in TFE 731

[cyork25]

Hey guys, I was just wondering how you guys are setting climb power in your TFE's? Are you using like for us (LR35) 795 all the way? Are you using 832 in the climb? Or are you setting the N1 numbers from the Max Climb Thrust chart? I've just heard a lot of different theories on this. Anyway, just interested to hear the responses.

 

[TXGold]

When I flew Lear 35s for a charter company, I used to climb at 810 or so max, and then 795 in the cruise. Some of the other pilots would go to 832 in the climb, but they were mostly the contract guys. The chief pilot once told me that he has seen some guys that fly 800 the whole time, no matter whether climbing or cruising. Only once did I see a guy get the charts out and dial in the N1 numbers. I was thinking to myself, are you kidding me, is this tool really doing this. But hey, maybe thats why 731s sometimes quit early.

 

[rice]

I believe the old Garrett 731 pilot tips book recommends that you use climb N1. In my old job we just made a small copy of the chart and laminated it for quick ref. in the cockpit.
Most 900 operators I've come across just use 900deg ITT as the gouge nowadays. Can't say thats the correct way but it is what it is.

 

[Shamus]

Climb at max. continous 832, and at cruise, 795 recomended if needed that high. Glance at the the N1 climb chart every once and a while. But your normal scan needs to be there, fuel flow and airspeed should be at the top as well. That's pretty typical for a 35, but as I'm sure you know, those engines are on almost everything, Lears, Falcons, westwinds, Hawkers, all over.

 

[cyork25]

Okay, here is the problem. We had mainly used the temps for climb, glancing at N1 every once in a while. Just make sure you are under 832, right. Anyway, we had a problem with one of our engines and it is on a "power by the hour" program. They are trying to say it was pilot error because we were a percent or so over the N1 chart. Anyway, they are not wanting to pay for the fix because of that, even though we were well in the green on everything. Just wondering your thoughts on this situation? Any help would be appreciated.

 

[TransMach]

731 Power Settings

Te real problem is that a lot of folks simply set thrust according to ITT. The 731-2-2B engine on the Learjet 35/35A/36/36A has a max continuious ITT of 832C and the manufacturer recommends that you reduce to 795C after 30 minutes. The correct method of setting climb thrust is setting maximum continuious RPM, at a temperature at or below 832C, or 795C after 30 minutes.

If you depart a low altitude airport in the winter, i.e. Chicago in January, you will see ITT temps of around 730-750 at takeoff thrust. Now, if you push it up to 795C you have just exceeded max RPM for takeoff thrust let alone max continuious.

This has been a problem for 20+ years and many operators have had the MSP folks, as well as JESSI decline repairs for crew induced damage.

You cold well be on the hook !

TransMach

 

[HMR]

You guys who set power based on temps instead of using N1 on the 731's, where did you learn this? It wasn't from Garrett and I doubt it was from the aircraft manufacturer.

How do you flight plan? How do you know what fuel burns you'll have on a transcon trip? I haven't seen charts in any jet I've ever flown that say "Fuel Flow @ 800 Degrees". I currently fly 2 jets with 731's (Astra and Falcon 50). When we fly it by the book we get book performance. Works great and keeps the mechanics happy. It's pretty easy to laminate a copy of the N1 settings and clip it on the yoke.


Disclaimer: I've never flown a Lear. Are the power charts temp based?

 

[cyork25]

well, we have N1 deecs so you push them all the way up for T/O. But anyway the manual says to set your N1 at 15000 ft, note the ITT and fly that ITT all the way up, as the alternate method to setting climb power, which we do!! But, I do know guys that fly 832 all the way up and never even pull it back to 795 after 30 minutes. The alternate method gives us temps between 810-820(maybe in the 20's on occasion). But It seems to me that the TFE will temp out before you will ever overspeed N1 or N2, but then again we have deec's, so i don't know what they run like without them.

 

[cyork25]

Oh, and sorry guys, I said in my above post that we glance at the N1. What I meant to say was, glance at the N1 chart, sorry about that.

 

[CandlerWun]

Interesting.

The numbers in the Westwind are totally different...870 max ITT in the climb, except above 30,000 (I believe) you leave the power levers where they are as long as they don't exceed max continuous ITT of 885. 849 for cruise.

Simuflite teaches using these ITTs for all power settings as an easy means of power management while simultaneously ensuring that N1 limits are not exceeded.

Josh M.

 

[TGTVS]

Run It To The Max, They Dont Call It The Grenade For Nothing!!!!!!!!!

 

[El Bucho]

In the Falcon 50 and 900 we use a small laminated copy of the N1's by atltitude and TAT. Have heard that you if you just fly the temps you can over pressure the engine case or something and start causing seals to leak/fail. I'm no A&P, just do what I'm told

EB

 

[falconpilot]

In the Falcon 50 and 900 we use a small laminated copy of the N1's by atltitude and TAT. Have heard that you if you just fly the temps you can over pressure the engine case or something and start causing seals to leak/fail. I'm no A&P, just do what I'm told

EB

SAME HERE... WE USE THE CHART.. HOWEVER WHEN I FLEW THE FALCON 10 I KEPT IT AROUND 800 IN THE CLIMB AND 785-790 IN CRUISE. THOSE TEMP SETTING SEEMED TO WORK WELL WITHIN CLIMB AND CRUISE N1. IN THE 50 AND 900 AND USE THE CHARTS ALL THE TIME. MAINLY CAUSE I WAS TOLD TOO, BUT ALSO THE S-DUCT MAKES THE CENTER ENGINE RUN A LITTLE DIFFERENT THAN THE LATERAL ENGINES. WHEN I FLEW THE LEARS I USED THE BOOK. MAINLY CAUSE I WAS IN A 31A AND YOU CANT GO VERY FAR ANYHOW, SO I TRIED MY BEST TO RUN IT BY THE BOOK IN ORDER TO GET THE BEST PERFORMANCE.

 

[blzr]

What model 731? Do you have DECS? Are you MSP Gold?

We have 731-3C, and DECS also insured by MSP GOLD, so we use MSP #'s not Garrett's. We usually climb in N1, but limit our temps to the low 870'2. Cruise is set after about 5-10 minutes after leveling at cruise altitude. Then it is strictly temp limited (PER MSP GOLD) to the Highest ITT not more than 850
and then match up N1's. Not as complicated as it sounds and we still get .78-.80 in cruise even with reduced power.

 

[TGTVS]

850 Was The Number Not To Exceed

 

[Raskal]

The different numbers for the 731's are interesting, in the hawker 700's its max cont at 885, the climb profile is 865 until 25000 then let it creep up to 885 max.

 

[OUPilot]

In the 35 with deecs at our company, it is normally full forward for takeoff, pull back to about 90 n1 for noise abatement till about 4000 agl, then set in about 800 itt. At 10,000 you can set n1 from the chart and let the deecs do the rest. Once level, let the thing speed up and then set 795 itt.

 

[HawkerF/O]

At 10,000 you can set n1 from the chart and let the deecs do the rest. Once level, let the thing speed up and then set 795 itt.

Exactly what is it that you think the DEECs are doing at this point? DEECs (N1) just keep the N1 from exceeding the manufacture's operational limts, typically when the power levers are full forward, but not always. What exactly is it that the DEECs are doing when you set the N1s then you say 'let the DEECs do the rest'? There's nothing for them to do. With N1 DEECs, your concern should be temperature, not N1. The DEECs are keeping the N1 in check, but they do nothing for the ITT. If you're operating by setting the N1s, then thinking the DEECs are doing something, you have not read the included documentation of the DEECs and/or you have been improperly trained and do not understand how the DEECs operate.

 

[OUPilot]

"The DEECs are keeping the N1 in check"

ok so when i said let the deecs do the rest...you are right, i should have said let the deecs keep the n1 in check. same thing. in the climb, make sure the itt is under it's limits, and check the chart every once in a while to make sure that the deecs are exactly keeping n1 where it should be. how's that? i guess i sorta assumed people know to keep the itt under limits.

 

[pettylear]

N1 deecs or not your still limited to the max N1 for climb chart in the AFM. 832 is your max ITT (period). There is no max N1 for cruise for the LR35/36. If you push it up automatically to 832 in the climb odds are 50% of the time your exceeding the max N1 for climb numbers. Ive found that setting 795 in cruise will ALMOST always keep you under the max N1 number. Once in cruise you can then fly 832 all day if you want (795 recommended after 30 minutes) - all this is goes off the same principles of a constant speed prop. *note* the max N1 for climb chart is also dependant on using the climb schedule 250 to .7, any faster then the max N1 chart isnt valid. Also just pushing the thrust levers to the stops to set takeoff power and let the deecs figure it out is a risky way to do things. Although the N1 deecs are much better they will still over shoot the N1 setting and re-adjust on the take off roll.