GregL, thanks for your clarification.  Have a safe and pleasant flight!

 

 

 

 

I never paid much attention to this switchover until I started flying a certain Brand-X T7.  It does NOT automatically switch to climb thrust in VNAV, with the result that the aircraft climbs at a very high rate, puts too much virtual wear on the virtual engines, and often busts the first altitude constraint.

 

Mike

You have no acceleration altitude selected. Normally it will be 1000' above the field. It must be put in next to the Flap setting. If not the engines will stay in take off power and never return to CLB.

 

The standard profile is take off thrust to 1000ft with V2 selected as the climb speed. At the Acceleration Altitude the aircraft will nose over and accelerate as long as a speed profile say of 250kts below 10000' is selected.

 

If flying manually then select Vref30 + 80 at AA to accelerate the aircraft manually. If the engines remain at TO power then press the CLB/CON button or FLCH to the cleared altitude. Both will engage autothrust.

@@scandinavian13 @@GregL Aha, got it! Thanks guys (-:

 

Also Greg, do you use True on the NAT's?

 

 

Aha, got it! Thanks guys

 

Welcome.

 

Also, I don't see a reason to use True on the NATs, though I'd defer to Greg for a more accurate answer.

Had a good look at it last night. Rather useful I must say. Often we do these things so many times it becomes 'habit' and therefore was quite a useful exercise to have a good look and re-familiarise myself with exactly what the FMS & Auto thrust is actually doing.

 

On the Thrust settings page you enter the de-reate temperature as given on the performance sheet taken from ACARS. This will give you D-TO and a temperature on Line 1 of the FMS. The computer will then select CLB, CLB-1 or CLB-2 for the thrust setting at take off depending upon weight, altitude of the airfield and ambient temperature.

 

Select the flap and the accel altitudes, enter the v1 and enter/confirm the Vr & V2 and put the MACTOW into the box for the stab trim.

 

Once on the runway the TOGA switches will give you the FMA 'THR REF' and the EICAS engine thrust limit will be set to CLB, CLB-1 or CLB-2. At 80kt's the FMA goes to HOLD and then after rotation and gear selection it reverts back to THR REF with the EICAS engine mode at CLB, CLB-1 or CLB-2. Once at level off (VNAV engaged throughout) it reverts to SPD.

 

That's the standard departure profile I flew last night.

 

NATS tracks are given with ITT between each point and must be flown in TRUE with TRK.

NATS tracks are given with ITT between each point and must be flown in TRUE with TRK.

Interesting! Will be doing so in the future (-:

 

 

The prime difference is that Roll Royce patented the use of Engine Pressure Ratio as a way of showing high bypass thrust. Hence GE can't use it. As you can see in the picture N1 is also displayed below the EPR figures.

Pratt and Whitney use EPR too and I'm sure they used it before Rolls Royce did, so I don't see how RR can have a patent on it.   RR (Bristol) used to use engine pressure difference as the basis of a percentage thrust indication.  Other RR engines used P7 (exhaust pressure) and RPM.  I believe the first engine RR used EPR on was the RB211 but I could be wrong.

 

On a high bypass turbofan N1 correlates quite well with thrust.  It really doesn't matter that much which parameter you use. The rated thrust limit (lb or kN) can be expressed as the equivalent in either EPR or %N1.

Ha yeah I know - just mainly for Derates etc I'm so used to using the percentage for N1, not sure what to use for EPR and what will be too much or too little.

Probably better not to think in terms of the %N1 reduction at all, but the assumed temperature and/or the fixed derate level that comes out of the takeoff charts.  So it's essentially the same process for PW, RR or GE engines. 

Had a good look at it last night. Rather useful I must say. Often we do these things so many times it becomes 'habit' and therefore was quite a useful exercise to have a good look and re-familiarise myself with exactly what the FMS & Auto thrust is actually doing.

 

On the Thrust settings page you enter the de-reate temperature as given on the performance sheet taken from ACARS. This will give you D-TO and a temperature on Line 1 of the FMS. The computer will then select CLB, CLB-1 or CLB-2 for the thrust setting at take off depending upon weight, altitude of the airfield and ambient temperature.

 

Select the flap and the accel altitudes, enter the v1 and enter/confirm the Vr & V2 and put the MACTOW into the box for the stab trim.

 

Once on the runway the TOGA switches will give you the FMA 'THR REF' and the EICAS engine thrust limit will be set to CLB, CLB-1 or CLB-2. At 80kt's the FMA goes to HOLD and then after rotation and gear selection it reverts back to THR REF with the EICAS engine mode at CLB, CLB-1 or CLB-2. Once at level off (VNAV engaged throughout) it reverts to SPD.

 

That's the standard departure profile I flew last night.

 

NATS tracks are given with ITT between each point and must be flown in TRUE with TRK.

 

Do you guys arm lnav and vnav before takeoff?

 

Alex

GE engines move a lot of air from the N1 fan around the engine so that may be the reason they prefer to use N1 as an indicator. Sort of like a turboprop , the engine thrust is converted to mechanical energy to spin the fan and the GE's in particular give a high percentage of thrust from it. 

 

Eric W

Do you guys arm lnav and vnav before takeoff?

 

Alex

Yes, after the thrust setting procedure the MCP is set up. If I expect to fly the departure as published laterally in the book then Lnav will be engaged. If I am expecting radar vectors after TO, especially in the USA, then runway heading will be selected in the MCP and Lnav left off. We always engage Vnav in order to get the correct noise reduction profile displayed on the flight directors during take off, even if manually flown. Vnav will also give you correct FD guidance in the even of a single engine failure.

NATS tracks are given with ITT between each point and must be flown in TRUE with TRK.

 

 

Interesting! Will be doing so in the future (-:

Hi Greg,

 

Not sure what you meant by "flown in TRUE with TRACK".

 

NATS are tracks between coordinates.

The FMC draws a greatcircle between those coordinates and since we have GPS on the 777 it flys a true track from one coordinate to the next.

As far as I know, this track can be and is normally flown with LNAV (not TCK SEL).

NATS tracks are given with ITT between each point and must be flown in TRUE with TRK.

 

 

Hi Greg,

 

Not sure what you meant by "flown in TRUE with TRACK".

 

NATS are tracks between coordinates.

The FMC draws a greatcircle between those coordinates and since we have GPS on the 777 it flys a true track from one coordinate to the next.

As far as I know, this track can be and is normally flown with LNAV (not TCK SEL).

I think you misunderstand me!

 

The aircraft is flown using LNAV BUT the tracks as promulgated by NATS are true tracks between the geographical waypoints.

 

In order to ensure that your track between the waypoints corresponds to your NATS clearance you select heading mode TRUE (in front of the LHS) and TRK on the MCP TRL/HDG selector so True track is displayed in the MCP window and on the ND track lubber line.

 

Once entering the NATS system you select an offset under SLOP (either R0, R1 or R2) and select IFF code 2000 30 minutes after crossing the NATS boundary. Once established a position report is required every 10 degrees unless the aircraft has ADS.

 

I hope that clears up any confusion.

Yes, after the thrust setting procedure the MCP is set up. If I expect to fly the departure as published laterally in the book then Lnav will be engaged. If I am expecting radar vectors after TO, especially in the USA, then runway heading will be selected in the MCP and Lnav left off. We always engage Vnav in order to get the correct noise reduction profile displayed on the flight directors during take off, even if manually flown. Vnav will also give you correct FD guidance in the even of a single engine failure.

 

Cheers man, You do this before pushback generally?

Cheers man, You do this before pushback generally?

Yes, load the route, request the winds, enter the SID, complete the critical data procedure, then check the D-TO on the FMC Thrust setting page, check it correlates to the EICAS engine page, ensure the flight directors are on, Autothrottles are armed, LNAV & VNAV engaged as required with V2 selected in the SPD window, runway hdg in the hdg window, blank in the FPA/V/S window and initial cleared altitude in the Altitude window.

 

Check the FMA's show V1 and V2 (generally Vr will be the same as V1 or hidden), Blank, TOGA (lnav white below if armed), TOGA (vnav white below if armed), Altitude constraint shows the MCP selected value, back in to the FMC to check departure runway and departure SID.

 

Then brief for the departure!

 

Pushback and go.

GE engines move a lot of air from the N1 fan around the engine so that may be the reason they prefer to use N1 as an indicator. Sort of like a turboprop , the engine thrust is converted to mechanical energy to spin the fan and the GE's in particular give a high percentage of thrust from it. 

 

Eric W

No more than PW and RR do.  All high bypass turbofans get most of their thrust from the fan.  GE have long used N1 for thrust setting, certainly dating to the CF6 engine.

 

Even on low bypass engines, N1 is a good relative measure of thrust.