B737NG F/D's on Initial Climb Out.

[172_driver]

172 Driver and flyboymike, the question as I see it is why the bars drop back from 20° to 15°, not why they are sometimes 20° and other times 15°

Agree.. but still think that "FD commands MCP (normally V2) + 20 kts and the pitch command will be whatever it will be" gives the answer.

To the OP, the other week it was very windy over Europe. Climbing into a 40-50 kts headwind I think the airspeed quickly increased to close to 200 kts (with V2+ 20 being something like 160-170). You can imagine the FDs climbed through the ceiling and were of very little use. Once the wind stabilized and airplane "caught up" with the energy gain the FDs slowly came back to center. I never pitched above 20 deg ANU because my company doesn't like it.

[Denti]

@ denti: if you use derate, plus max assumed, you FD's will still give you a correct pitch control. Ofcourse not at rotation, but in initial climb. Thanks, I have a FCTM.

Then i humbly suggest to read it, your post above said something else:

You will get an original pitch up indication of 15 degrees NU.

This should result in a V2 plus 20 speed.

That is of course not always correct, actually quite often. 15° does usually not result in V2 plus 20. However, after initial pitch up to a achieve said speed the flight director will shortly follow and indicate the same. If one uses it at all.

You probably switch them off during TO, no?

Sometimes i do, sometimes i don't. As the company actively encourages us to fly without FD and autopilot to keep ones scan and skills it is up to us what we use.

And, while during an CatIII landing, make sure you look through them, just to be sure?

Monitoring if the autoflight system does its job? Of course, that is what i am paid for after all. Theoretically from 200ft until taxi speed we can go to sleep though as any failure (including engine failures) will result in a safe landing and rollout, but of course we still monitor the system as dual failures still can lead to unsafe conditions.

[latetonite]

Ok Denti,

I see you try to negotiate a lot.

In an answer to point one. My post above did not say something else. I presume we are not discussing rotation here.
I do read the FCTM quite a lot. In fact I am teaching from it 5 days a week.
Even the misconceptions I point out.

Second quote: If I read your comment well, your are suggesting the FD will follow the pitch you are flying? You do not believe that yourself, Do you?

Point three: your company does encourages TO without FD? And you practise that to prove you can rotate better, counting three degrees per second? I hope you are aware that your fellow new copilots will probably crash doing this in LoVis TO, given the remote condition that an engine fails.

I trust you make a note in your speech to the passengers, that they are lucky today in this bad weather that they have a good pilot who does not put trust in his instruments, and is honing his hand skills a bit.

In the last referral, catIII landings, you monitor failures of the 'system', you said.

But you trust letting the FDs command the autopilot, and land your flying machine, even on one engine. We have those planes too, but me maybe being not so talentfull as you, I do not see if the FD shows correct pitch. However, as we have two FDs , with two FCC behind them, I trust them. And let them bring me safe to the ground.

Not believing the FD during TO, but betting your life on them during autoland in LoVis, is a bit hypocrite, I think.

[flyboyike]

Originally Posted by latetonite

Point three: your company does encourages TO without FD? And you practise that to prove you can rotate better, counting three degrees per second? I hope you are aware that your fellow new copilots will probably crash doing this in LoVis TO, given the remote condition that an engine fails.

I would hope the new copilots' not crashing after an engine failure wasn't dependent on the F/D. After all, it can fail, too.

[172_driver]

latetonite,

To me it sounds like you want to misunderstand on purpose here.

I too think the FDs can be a bit over-sensitive on initial climb out and by looking through them, setting the attitude you think will be right for the weight/thrust, the FDs will usually come to sense and settle down quite close to where you put the nose.

[sheppey]

quote: Sometimes i do, sometimes i don't. As the company actively encourages us to fly without FD and autopilot to keep ones scan and skills it is up to us what we use. quote:


That cheers me up greatly. At long last a company that actually encourages its pilots to minimise automation addiction by flying normally, rather than by the magenta line.

[latetonite]

Sheppy, got your point. But there is no magenta line on my FD.

We are discussing TO here. In a modern airline with pax onboard.

Really want to see the airline which encourages raw data TO in daily operations.

Not that I do not know how it goes: In my career I have been flying 3 commercial A/C types as PIC, not even equipped with a F/D.

And quite a few more without an FMS.

[RAT 5]

B737NG PILOT:

I'll add my tuppn'yworth for your consideration. First: DO NOT rotate into the FD. Rotate to an attitude; i.e. look through the FD. The target is 15degrees. The FD commands a minimum of V2+15 to a max V2+25. This is on climb-out after the gear is up. Hence the initial target attitude. You will find that if you select a thrust which equals your weight, i.e. you use minimum thrust the FD will stabilise at 15 degrees eventually. If you over rotate the IAS will be <V2+15 and the FD will lower the attitude to accelerate to V2+15 then climb-out at that speed. If you under rotate, or rotate late, the IAS may be >V2+25 and the FD will eventually guide an increase in attitude to reduce IAS back to V2+25. It will then most likely stabilise at 15 degrees again. If you rotate properly you will find that you are at V2+20 and the FD will maintain this with 15 degrees NU.
If you use more than minimum thrust the initial rotation is still 15 degrees, but the excess thrust will allow a climb-out at V2 +20 with higher than 15 degrees. The FD will guide this attitude. It looks at many performance parameters to give correct guidance.
If you rotate such that the speed at liftoff is >V2+25 beware and DO NOT rotate to FD's as this will cause a rapid drop in IAS and a porpoise pitch climb-out. Above 20 degrees the drop in IAS is VERY rapid; and why would you want to go above 20degrees? Either you have screwed up the rotation and be at too high IAS, or you are way over powered. Either way your initial climb-out trajectory will be more than enough. If you are at so high an attitude the IAS will reduce quickly and then the FD will command a strong reduction in attitude to maintain V2+25. This can be quite uncomfortable.

A single continuous rotation at the correct rate to 15degrees, started at Vr should result in V2+20, and after the gear is up you'll find the FD maintains this with 15 degrees is weight matches thrust. Be aware if you are over powered and then the resulting extra 1 or 2 degrees is not confusing. BUT always use the initial 15 degrees.
Note" this is for F5 takeoffs. F15 may be 1-2 degrees lower.

[Lord Spandex Masher]

and why would you want to go above 20degrees?

What's wrong with going over 20 degrees if you need it?

Either you have screwed up the rotation and be at too high IAS, or you are way over powered.

Occasionally I am required to carry out a full power take off in an empty, and I mean empty, aircraft with 5 tonnes of fuel on!

Either way your initial climb-out trajectory will be more than enough.

In the above case you need the pitch to control the speed otherwise you get very close to the flap limiting speed before you can say P45.

[latetonite]

There is some truth in most replies, however, be aware that your carefull calculated V speeds go immediately out of the window if you do not rotate and climb correctly.

[RAT 5]

Occasionally I am required to carry out a full power take off in an empty, and I mean empty, aircraft with 5 tonnes of fuel on!

In the above case you need the pitch to control the speed otherwise you get very close to the flap limiting speed before you can say P45.

Why do you need to maintain full power for so long. Reducing power would allow reduced attitude etc. I hope this was performed with a very high SID cap. The vision of a home sick angel comes to mind. It used to be that a regular full power takeoff was required to confirm it was available and test the engine. Surely you don't need to maintain it for the full 5 mins. If not then you could reduce power to something more appropriate. I would have thought full power with a very light a/c was more a test pilot manoeuvre. Full power confirmations could be done easily by a line pilot on a more normal loaded a/c. This occasional testosterone fuelled takeoff might not be allied to the original question, which I'm sure was more line orientated on a normal day.

[Lord Spandex Masher]

My point is that there are no dragons beyond 20/25 degrees. It's not an upset and it's not dangerous. Most opinions are that exceeding 20/25 degrees pitch causes voodoo to happen. I'm just highlighting that it doesn't.

I'm required to carry out these take offs as part of an air test schedule but as we fly with standard line FOs we have to use standard procedures and there're other parameters to be monitored whilst at full power.

I accept that that isn't relevant to line ops and that I've strayed from the original topic but occasionally your line pilot will be asked to ferry or position an empty aircraft and may need to use full power. I think it's important to highlight that you won't fall out of the sky if you exceed 20 degrees and quite often it makes your day a lot easier if you do.

[BOAC]

I think the 73 Jurassic used to say
"Limit pitch to 20 degrees for passenger comfort"

Of course, when your 'pax' were sitting on trays.................

[latetonite]

Notwithstanding the passengers and crew in the cabin, I would not mind pitching 45 degrees NU, if it would result in a steady V2+20.

[RAT 5]

While your at it why not roll and pull through for a reverse cuban 8?

[flyboyike]

In the US it's called the Greater Antilles Eight, due to the embargo.

[latetonite]

Personally, I would not mind. At least something different.

[Denti]

We are discussing TO here. In a modern airline with pax onboard.

Really want to see the airline which encourages raw data TO in daily operations.

What is so special about it? It is basic airplane flying 101. Is the training in your company really so bad that they cannot trust their own pilots to do basic airplane handling? I don't doubt that you're able to do it with your background, but SOPs that actively discourage pilots from basic flying are a sure sign of a huge training deficit.

Just for reference, that is what our 737 FCOM says under the header Autopilot/Autothrottle Policy:

Continuous use of automatic systems leads to loss of basic knowledge of power settings/pitch attitudes and reduces the ability to fly accurately with a low workload. Pilots should therefore regularly fly the aircraft manually, with emphasis on manual departures/ approaches with and without the flight director.

Some never use the FD except during low vis operation (FD is not required for AP usage), some take a more moderate view and do every now and then take offs and approaches without using the FD.

Quite true by the way that wrong rotation and initial climb out can invalidate performance figures, our -800 performance is based on 2°/sec rotation rate and the -700 on 2,5°/sec. Unlike during the classic days we do not fly the short version (600) as it doesn't make any commercial sense, but performance would be based on 3°/sec.

[Aluminium shuffler]

First of all, there is nothing wrong with prudent and appropriate raw data departures. Some people seem to think that the wing bolts are connected to the FD switch. If Boeing thought that raw data flying was dangerous, they wouldn't fit the switch... Suggesting that all the performance calculations are nullified by flying raw data displays an immense lack of confidence in the individual's flying ability as well as their understanding of how everything works.

Secondly, the received wisdom is that the pitch attitude is not to exceed 20 degrees NU. The reason for this is to give you a decent opportunity to get the nose down without rapid speed loss if an engine fails and also to allow for wind sheer - it has nothing to do with comfort levels. Going beyond 20 degrees is needless and most companies' OFDM systems would be pinging off. I certainly wouldn't be happy with a colleague who did it without very good reason. Pitching higher sounds like show boating to me.

Third, the FD initial 15 degree NU command is only a rudimentary aiming point for rotation, and it guarantees nothing. It is a conservative pitch angle which will be modified once the FCCs catch up with the aircraft's actual performance. Commands above 20 degrees should only be followed to the 20 degree line.

Fourth, any pilot that blindly follows the FD without "looking through" it to verify against the performance data that suitable attitudes are being commanded is a fool. FDs are very useful but not infallible and they are reactive, not pre-emptive.

Fifth, FD commands aren't always displayed proportionately - if the FCC thinks you are not responding fast enough, the commands become exaggerated to gain your attention., and if you follow them fully you will be over-controlling the aircraft.

[Centaurus]

Fourth, any pilot that blindly follows the FD without "looking through" it to verify against the performance data that suitable attitudes are being commanded is a fool. FDs are very useful but not infallible and they are reactive, not pre-emptive.

"Looking through" the flight director presentation is quite difficult since most of the time the FD is being used means the pilot is concentrating on keeping the needles centred and watching for the slightest vertical or lateral movement. In my experience many new pilots to type are spooked as they try to centre the needles and because of their intense concentration on needles in a tiny square symbol on the ADI, they lose all awareness of the true pitch attitude behind the needles.

This is especially so when conducting an engine failure at VR. The fact is very few simulator instructors whether current check pilots or not - will take the trouble of hopping into a control seat and actually demonstrate how to fly the engine failure. They are mostly perfectly content to watch the candidate lose the plot due to chasing the FD needles, over or under controlling on elevators, ailerons and rudder pedals and then from the back of the simulator, loudly criticise the candidate. Or just as bad, try to "talk them through"

IMHO if you have to resort to "looking through" the FD display in order to see the real nose attitude hidden behind the FD needles, then it is better to immediately switch off the FD to get a clean unobstructed look at the ADI attitude. Then at leisure turn the FD back on when it suits. FD's are an over-rated instrument system that have the potential to, and have led to, loss of instrument flying situational awareness