A few More Questions... Coming Along

[drewhosick 0]

Hi there,

 

I had originally posted 100 questions topic because I was very lost. Starting to get the hang of this beast but I do have a few more quick questions.

 

1. Procedure with RNAV and no ILS... When you're about to land you disconnect the Autopilot obviously, how about the throttle. Is the correct procedure to turn it off or is there a way to set 5 above reference speed during the RNAV approach? Just wondering because when I've tried it a few times previously to use the Autothrottle all the simulation does is speed up the engines to keep me from landing. I assume I should be disconnecting it.

 

2. I have found at least on 3 or 4 occasions that my flight won't allow me to meet what the FMC needs in terms of a descent. I know about the speedbrake and drag thing but why is it the FMC automatically programs impossible vertical routes.. also why is it that if you're say 40 miles away of a point or even 80 it won't desend quicker to make the marked altitudes. It's like sometimes the FMC will descend at 800 ft/m instead of doing more to get down quicker and then later in the same stage it will go to 1600ft/m... Kinda strange, am I missing something?

 

3. Speaking of the FMC. I remember in the tutorial you can add codes to speed restrictions and altitude restrictions. Where is there information on the different ones in the manuals? I'm having a hard time finding answers in these massive books of information.

 

4. Finally... For the first time in a long time I ditched a plane(yes in this case the 737ngx) into the water as I overdrove my landing at TNCM. Short runway I know but it leads me to 2 questions, is there a trick to shorter runways? Just more flaps/max speedbrake obviously and max autobrake? And for the takeoff, where can I find in the manual information on getting the max out of the engines. Tried taking off from TNCM twice. The first time wasn't pretty, I think I ripped off the back landing gear on the airport fence because it wouldn't go up with the rest of the gear. I didn't know about the whole derate not giving me enough kick to get up in time there and I was fully loaded practically with a long trip to Tulsa and a pretty heavy load as well. Is it just leaving derate off that will get me maxed out on power or is there a way to force more power out of the 737 because I joined a VA that has my hub at TNCM so I figured I'd better learn to takeoff and land on shorter runways.

[Fabo 213]

1. Procedure with RNAV and no ILS... When you're about to land you disconnect the Autopilot obviously, how about the throttle. Is the correct procedure to turn it off or is there a way to set 5 above reference speed during the RNAV approach? Just wondering because when I've tried it a few times previously to use the Autothrottle all the simulation does is speed up the engines to keep me from landing. I assume I should be disconnecting it.

 

You are always supposed to disconnect autothrottle when disconnecting autopilot. It is not a "hard" restriction, but a strong recommendation. Anyway I suppose by ILS you mean Autoland, which means that autoflight will expect to do all the work, including landing flare maneuver with throttle retardation. It does neither in Approach mode, ILS or RNP.

 

 

2. I have found at least on 3 or 4 occasions that my flight won't allow me to meet what the FMC needs in terms of a descent. I know about the speedbrake and drag thing but why is it the FMC automatically programs impossible vertical routes.. also why is it that if you're say 40 miles away of a point or even 80 it won't desend quicker to make the marked altitudes. It's like sometimes the FMC will descend at 800 ft/m instead of doing more to get down quicker and then later in the same stage it will go to 1600ft/m... Kinda strange, am I missing something?

 

FMC assumes no wind, unless you tell it what wind there is. If there is a higher than expected tailwind, you will have problems keeping up with computed track. Also, if you have antiice on, and have not told the FMC you would, it will affect the calculated and actual performance.

 

4. Finally... For the first time in a long time I ditched a plane(yes in this case the 737ngx) into the water as I overdrove my landing at TNCM. Short runway I know but it leads me to 2 questions, is there a trick to shorter runways? Just more flaps/max speedbrake obviously and max autobrake? And for the takeoff, where can I find in the manual information on getting the max out of the engines. Tried taking off from TNCM twice. The first time wasn't pretty, I think I ripped off the back landing gear on the airport fence because it wouldn't go up with the rest of the gear. I didn't know about the whole derate not giving me enough kick to get up in time there and I was fully loaded practically with a long trip to Tulsa and a pretty heavy load as well. Is it just leaving derate off that will get me maxed out on power or is there a way to force more power out of the 737 because I joined a VA that has my hub at TNCM so I figured I'd better learn to takeoff and land on shorter runways.

 

TNCM is by no means a short runway for a 737 to land on. 737-800 will land and stop on it with flaps 30, no wind, 30 degrees, Q1013, wet runway on maximum landing weigth. You need to use a proper landing technique though - positive landing in touchdown zone. No floating for a mile to grease her down. -400fpm is OK. Also, use manual braking, or AUTO 3 or MAX. Spoliers should be ALWAYS armed before landing. Reverse thrust will not affect landing roll if you use autobrake, but will shorten it if you use manual braking.

 

As for take-off, there is only a general information section in FCOM, PD chapter. If you want to be sure about safety of your take-offs, the best is to invest into TOPCAT, or find a TO perf calc tool by Israel D Oleo (hope that is how it was...) here on the forum. Anyway a small guide that will help you get your plane out, even if almost full:

-Use flaps 15 for RW28 or flaps 25 for RW10. It will climb worse, but get off the runway sooner. TURN HARD RIGHT IMMEDIATELY after taking off from 28 though - you do not want to hit that hill.

-Trim! Trim! Trim! You will have a big problem getting the aircraft up if it is not trimmed as it should be, according to FMC.

-Dont be afraid to bump the engines. Select 27K rating on N1 page. (for 800)

-Last, but very important, use correct take-off technique as described in FCTM, very basically, as you hear "Rotate" call, move fluidly, but energically, the yoke towards yourself, aiming to achieve about 3°/s rotation speed. Aim for 10° at first to avoid tailstrike, when you have positive climb, gear up and follow FD to V2+20. This technique makes for safe, fluid, and fast take-off.

[tommchowat 1]

1. Procedure in my company is to always disconnect the autothrottle first, then the autopilot. So when you decide to take over, double press on the AT disconnect, double press on the AP disconnect. Theory behind that is because they don't really want us flying with AP out and AT in. Pitch and power couples are a bit different with the plane taking care of the thrust.

 

2. As said above, wind, QNH, anti-ice in the forecast page will probably help with this. I find the NGX is pretty good at keeping a VNAV path all the way down, has the occasional blip after a waypoint but fixes itself. Have a look on the FMA and make sure you're in VNAV PTH, not VNAV SPD. In path mode, the plane is hell bent on keeping the calculated path and doesn't give a crap about speed, so keep an eye on it. In speed mode, the opposite is true. Use the path deviation indicator on the right of the ND to crosscheck where you are in relation to where you should be. Sometimes the FMC will give you a message like "STEEP DES AFTER XXXX". If it says that, then just anticipate. It's quite common on a few arrivals into London Gatwick.

 

3. Not really sure what you mean here.

 

4. In addition to what Peter suggested above, doing a no engine bleed takeoff is what we do if we need even more thrust than 26k can give us.

[Spin737 102]

2: There is an issue with the throttles and the making sure they are at idle. Use the keyboard shortcuts to force the engine to go to idle every so often or cycle the throttles.

[drewhosick 0]

Thanks so far to both of you. Tom, you lost me there when you said FMA.. and ND? Should know the short forms but I'm blanking on both.

 

Also for 3... In the tutorial they said to append something like A or B or something like that to the speeds or altitudes(for example to make sure it's at or above that altitude)... How do you recode those in the route? Is there a place in the manual that covers everything in the FMC including those codes that you can append?

[tommchowat 1]

Sorry, FMA - Flight Mode Annunciator (Top of the PFD) and ND - Navigation Display (inboard display unit).

 

I don't really know what you mean by 'record those in the route'. If you need to check or amend them, then go to the legs page, and they'll be on the right hand side.

 

Example, if a point has a speed restriction of 220 knots or below and at or above FL80, on the right would be "220B/FL80A". If you wanted to change this to say, 250 knots, you would enter "250/".

[Fabo 213]

Tom, he meant XY alt or above (120A) and YZ or below (210B) on 3. I dont feel like looking it up in FCOM/FCTM right now so... maybe someone else does and tells us chapter and page.

 

Drew, FMA is Flight Mode Annunciator, the part over the artifical horizon that tells you which autoflight modes are active. ND is the navigation display.

[drewhosick 0]

Example, if a point has a speed restriction of 220 knots or below and at or above FL80, on the right would be "220B/FL80A". If you wanted to change this to say, 250 knots, you would enter "250/".

 

What I mean is what are the different codes you can use to "write over" what the route has... Above you say 220B/FL80A I'm talking about the B and A here. What are all the codes and what do they all do when planning your route. In other words, how can I tell the FMC to make sure I'm flying at or below 220kts past a waypoint and beyond? Is it just A and B? A = speed or altitude and above and b - speed and altitude or below? I was never able to find this info... And seing you write B and A it just clicked that it might stand for above and below but I didn't know this. Is that correct?

[tommchowat 1]

If you want to tell the FMC that you want to be at or below 220 knots by a waypoint, find that waypoint in the legs page, then enter "220B/" on the right hand side next to it! Then, as long as you're in FMC SPD and not SPD INTVing or anything, it will command a speed reduction just before reaching that waypoint so you'll be on the right speed as you get to it. Magic! Altitudes/flight levels work much the same.

 

And yes, A is at or above and B is at or below. Not so much a code, fairly simples

[Spin737 102]

I don't think you can "at or below" or "at or above" airspeeds, only altitudes. You can "at" airspeeds, otherwise VNAV will figure out what speed you should be at.

[tommchowat 1]

You can do it with airspeeds.

[Spin737 102]

You can do it with airspeeds.

Ah, so you can. I've never seen anyone use it.

[japascoe 98]

Yup, done it a few times on the STAR into EHAM, where there's a constraint of 250 kts max at 10,000' at some waypoint. The FMC has that encoded as 250/FL100 (TA is 3000') and then complains because it wants to be at 240 kts due to the overall rule (displays UNABLE 250 KTS AT X). Changing the constraint to 250B/FL100 fixes the problem.

Probably not real world technique

[tommchowat 1]

We change the restriction in the DES page to 250/FL100. Default is 240.

[Spin737 102]

Yup, done it a few times on the STAR into EHAM, where there's a constraint of 250 kts max at 10,000' at some waypoint. The FMC has that encoded as 250/FL100 (TA is 3000') and then complains because it wants to be at 240 kts due to the overall rule (displays UNABLE 250 KTS AT X). Changing the constraint to 250B/FL100 fixes the problem.

Probably not real world technique

We change the restriction in the DES page to 250/FL100. Default is 240.

We did that at one of my airlines in Asia.

 

The UNABLE 250 AT XXX doesn't seem to happen in the places in the States where I fly much anymore.