737NG - Trimming in the flare??

[Devils Martini]

http://www.flightlevel350.com/Aircraft_Boeing_737-700-Airline_MALÉV_Hungarian_Aviation_Video-7460.html

Saw this video on the web and once the flare begins (around about 2:45 in the vid) you can hear the trim being wound on in the background. This then stops as the main gear touches down. I am assuming here that nose up trim is being applied since it is the flare.

Can't find anything in my FCTM about this, seems a little dangerous at low level, surely an increased risk of tailstrike on the longer NGs if you overcook it? More difficult to judge flare? Lots of nose up tendency if balked landing? Just wondering if anyone can shed any light on this.

Cheers,

Devils Martini.

[FlightDetent]

I definitely cannot. But I know that a local operator once had a t/s because of trim-to-flare technique.

[Drop The Dunlops]

Yep, that's definitely the trim in the flare.

Not sure what date the video was taken but it appears to be a hot sunny day in Athens. If you look carefully you can see the crew have used Autobrake 3 and idle reverse.

Hope the turnaround time was generous.

[Doors to Automatic]

If you look carefully you can see the crew have used Autobrake 3 and idle reverse.


Why on earth would they use AUtobrake 3 on a 4000m runway?

[Rainboe]

Running late..... making a turnoff....saving time....local regulations....unserviceability. 737 brakes are effective and don't suffer heating problems. The NG has a trim system that fires off by itself, without input, especially just after take-off.

It's almost enough to put you off having visitors filming on the flight deck (now that it is forbidden anyway). If these pilots knew how that visit was raising suspicion of their operating practices, they would never allow it again (not that they should have this time). They are well trained- why not leave them to fly it as they think right?
PS I've done Autobrake 3 and Idle reverse- there are reasons. Instead of implied criticism, I think it would sound better if comments were phrased 'I don't understand why they........, could someone explain please?'

I would never allow filming up on the FD. One of my colleagues had a little girl visitor on his lap, and he allowed her to touch a switch. Another visitor photographed it and hawked it around the papers. He spent nearly 6 months about to lose his job, getting a reprieve very late. It spoilt his career end. In a way, it's better these days that visits are not allowed if such criticism can arise from them!

[Funnel Cloud]

Running late..... making a turnoff....saving time....local regulations....unserviceability. 737 brakes are effective and don't suffer heating problems.

Hi Rainboe,

I agree indeed, the NG brakes are very good and I have also used Autobrake 3 with idle reverse before. It's not a big deal especially when you're operating at light gross weights, however.... you should still be very aware of the minimum brake cooling schedule. Nobody says that these pilots didn't do that, because they may have had a nice long turn-around anyway. In that case there is no problem.


The NG has a trim system that fires off by itself, without input, especially just after take-off.

Indeed this "SPEED TRIM SYSTEM" works especially just after take-off but NOT during the landing flare. It's only armed at high power settings (N1 greater than 60% for the -800). I have never seen a trim wheel move during the landing flare and according to my FCTM it's not recommended.

I must say I agree with the rest of your post. It's sad that you can't trust anyone these days and it seems that any normal looking pax could be a journo. Some colleages of mine also allowed a passenger taking a photo of the flight deck during disembarking. The next day it was all over the newspapers with the title "Journalists gets unrestricted access to flight deck of passenger jet" or something like that. :ugh:

Cheers,

FC

[Rainboe]

It's not a big deal especially when you're operating at light gross weights, however.... you should still be very aware of the minimum brake cooling schedule.
Having flown the 747, I am extremely aware of the brake cooling schedule. However, that aeroplane was flying Budapest-Athens, not a short leg, and would be returning. So brake cooling on a 737 would not be a factor here. Reverse power not encouraged unless needed due wear. Perfectly reasonable! So that's why, on Earth, they used Autobrake 3 and idle reverse on a 4000m runway! Some people can't just view it for what it is, they just have to try and find something to criticise. It's this that makes me think it better the public never looks in on the FD again!

[omnidirectional737]

From the QRH at 60 tons and 30 degrees and brakes on speed of 140 knots recommended brake cooling schedule is about 40 minutes with Autobrake 3 and no reverse thrust and No special procedure required with Autobrake 3 and two engine reverse thrust.

[Rainboe]

So the problem is, Doors>Automatic?

I don't understand the trimming in the flare. I thought maybe it was an autoland, but no autopilot disengage tone was heard.

[Fiske]

Hi,

I would suggest that the fact it was a long flight has nothing to do with the brake cooling schedules, the turn around is the critical time factor in case you have an RTO.

I think this is what people are getting at Rainboe, but I also think you're right. Why should people critise these pilots when they know nothing about this particular flight, loads turn arounds etc

:rolleyes:

[Rainboe]

I know about brake cooling thanks! I've lost 4 tyres at LHR on a high speed abort.
Before the famous Pprune Court Martial convicts these guys, let's remember they appear to be able to run a regular operation without appearing in the news with overheated brakes everywhere. I'm not sure what the loads Budapest-Athens are like, but they were probably quite light, and returning on that leg, there is plenty of time for brake cooling. 3 Autobrake/Idle reverse is quite a common selection for landing- I use it myself many times. Power above idle is not always encouraged for wear and noise reasons.
So let's, people, enjoy the video for what it was- a very generous opportunity to allow videoing on the flight deck (which they shouldn't have allowed) and not use every available possibility (and manufacture some) to attempt to find criticism!

[propnut]

There is an autopilot stab trim command that will run the stab trim nose up as it starts the flare manouvre, just before touchdown. See Maint manual ref: 22-11-00 p 98.112.
It occurs for 5.5 secs when:
a/c in the air and in flare mode of DFCS and,
not in GA mode and,
G/S is engaged.

It is not easy to remember as there are a lot of things that can cause stab trim to function at different times.

regards,
Propnut







Hi Rainboe,

I agree indeed, the NG brakes are very good and I have also used Autobrake 3 with idle reverse before. It's not a big deal especially when you're operating at light gross weights, however.... you should still be very aware of the minimum brake cooling schedule. Nobody says that these pilots didn't do that, because they may have had a nice long turn-around anyway. In that case there is no problem.




Indeed this "SPEED TRIM SYSTEM" works especially just after take-off but NOT during the landing flare. It's only armed at high power settings (N1 greater than 60% for the -800). I have never seen a trim wheel move during the landing flare and according to my FCTM it's not recommended.

I must say I agree with the rest of your post. It's sad that you can't trust anyone these days and it seems that any normal looking pax could be a journo. Some colleages of mine also allowed a passenger taking a photo of the flight deck during disembarking. The next day it was all over the newspapers with the title "Journalists gets unrestricted access to flight deck of passenger jet" or something like that. :ugh:

Cheers,

FC

[sarah737]

. The NG has a trim system that fires off by itself, without input, especially just after take-off.


Only if you are to late to trim yourself and you have to much pressure on the yoke!

[FCS Explorer]

737NG FCTM clearily says:

Note:
Do not trim during the flare or after touch down. Trimming in the flare increases the possibility of a tail strike.

and one more thing:
on an CAT II/III auto land there is an auto-trim bias. but not during landing flare, it happens at around 400 AGL.

[cowabunga438]

Autobrakes 3 pulls the NG up very quickly. Almost uncomfortably quickly. I rarely use it even when trying to make the first turnoff.

The use of idle reverse and autobrake 3 will use the same runway length as full reverse and autobrake 3.

[Rainboe]

Nobody disputes that. However it's not nearly so quiet. And who says it is 'uncomfortable'?

[VONKLUFFEN]

....just ask the pax. Specialy those who are really afraid of flying.

[Telstar]

cowabunga438 & VONKLUFFEN, I quite disagree. While traveling as a Pax on one of our company aircraft recently I was very impressed with how smooth and comfortable an idle reverse/High Autobrake setting landing was. It is much more gradual and progressive in deceleration. Since that flight, strictly according to ALL conditions I Endeavour to use this technique. Our company also encourages us to use this technique subject to all conditions as it is cheaper for them in the long run to use the brakes.

Trimming in the flare is a no no:

Boeing FCTM Chapter 6- "Landing"

"Do Not Trim during the flare or after touchdown. Trimming in the flare increases the possibility of a tailstrike"

[BOAC]

Bringing the thread back 'in trim':) , propnut is correct, and FCS explorer is only partly so. On a dual channel approach, with 'FLARE' armed, the a/p applies an additional nose-up trim at about 50 Radio.

I have not watched the video but I guess that is what is seen?