Usage of speed brakes, v/s, etc.

[Microburst2002]

Speedbrakes must be used if needed, we all agree in that, I'm sure. Only you have to think first if you really need them before using them.

I see speedbrakes as "energy dissipators". I will mot use them if I don't have excess energy, normally. Of course there are exceptions, like not too reasonable ATC requests or times where you need a very quick speed decrease without reducing you rate of descent.

Use of V/S at high altitude (a common practice even by those pilots who are afraid of it in other circumstances), can be very tricky. Mostly it is used in the bus when approachin crising level, this being at or above optimum, or near pmaximun, since the rates are so low and "oscillatory" that it seems better to keep a reasonable fixed rate at the expense of a few mach centesimals. But beware of doing this in a day where VMO and VAPROT are very close, specially after a "reach FL 380 before ZZZ". Don't let the airplane be at green dot, where the slide down the backside of the curve begins...

[Intruder]

Also, since you bring it up intruder.
I have done it once in the sim only, intercepting GS from above.
Arm the approach, turn alt knob to be higher, select V/S -1500-2000 and pull.
Use speed brakes to help?

DO NOT set a higher altitude when intercepting the G/S from above!!!

Until you capture the G/S, keep a reasonable altitude in the MCP. In this case, the ILS minimums might be appropriate if you are inside the FAF or any other fix with an altitude restriction. You might also use 1000' above the airport, because if you haven't captured the G/S before then, you won't meet Stabilized Approach criteria.

AFTER you capture the G/S, reset the altitude to Missed Approach altitude.

Use speedbrakes only if needed to keep A/S under control AND if allowed with landing flaps.

[Capn Bloggs]

Originally Posted by Whysotough

Line training captain today told me he personally never uses V/S to increase ROD generally because it disregards speed

Training captain? Not a very good one. I do not like using Level Change/FLCH/Open Desc (I think it is called on the Airbus), when close to configuring and close to the ground. Unless you're a rocket scientist, it is hard to predict what sink rate the aircraft will develop. The beauty of VS (or FPA for the backward Jungle Jet) is that you can directly control your sink rate. If the speed starts increasing beyond desired, pull out the speedbrakes! If the workload is too high and the autothrottle then starts powering up, who cares?

The classic use of speedbrake is Intruder's scenario: capturing GS from on high. Set a controlled ROD (~1500ft) and wait for GS capture. Of course, you keep configuring as per normal - if speed reduction doesn't occur, pull out the speedbrakes. Selecting Level Change/FLCH/Open Desc is asking for very high, unknown rates of descent, which, if for some reason you miss the GS could be very scary. This also applies when high on a NPA. VS directly controls the ROD=good.

Another scenario I frequently encounter is ATC holding you up inside 20nm and then clearing you down. VS will make the aircraft descend; the other modes do not if you are reducing speed whilst configuring. If not in VS/FPA, the aircraft only descends only when it gets to the target speed. Pulling out the SB then just makes the nose bury.

Finally, as mentioned previously, VS is the nose-position mode. I want immediate nose response now eg bumpy cloud approaching (or TCAS traffic): VS is the way to do it (unless you have a direct pitch mode, of course).

[Capn Bloggs]

Originally Posted by Intruder

DO NOT set a higher altitude when intercepting the G/S from above!!!

Originally Posted by john smith

Airbus SOP (and SOP at both my previous and current companies) is to set a higher altitude than the current aircraft altitude on the FCU to prevent ALT* mode, during an intercept from above.

That's real smart. Miss the GS for whatever reason and you just keep going until you hit the ground.

At what point does your SOP mandate you convert your "ILS" to the LLZ approach, or disconnect the AP and manually get back on the GS, or do you just fly down the ILS/GS in VS?

I suggest that if you/the aircraft is sufficiently out of control not to be stabilised on the approach, with GS captured, you shouldn't be there at all. Setting the ALT SEL high removes that only protection you have. Our SOP is to set the ALT SEL at 1500ft AAL. If you haven't captured the GS by then, you must convert to the options I mentioned above or Go Around.

[felixthecat]

In an intercept from above would you not set say a stabilisation altitude…say 1000 feet and then if you get ALT capture whilst trying to capture the GS your not stable and you go around? If you set a higher altitude (say the go around alt) you are possibly too busy trying to capture the GS with a high ROD near to the ground you don't notice the altitude for a moment and hey presto WHOOP WHOOP PULL UP, SINK RATE SINK RATE or worse Without having something sensible set when do you call it a day and throw away the approach? 1000, 500, where?? I personally like to use the automatics as a safety net for my own incompetence

I personally would only set a higher altitude when I am established on the GS and the situation is 100% under my control…..

[macdo]

John_smiths sop is the standard AIRBUS and is certainly the SOP in my outfit. The problem is, if you don't get the FCU well out of the way, the opaque methodology by which Alt* operates means you end up with multiple alt* captures which prevent you from getting VS going. All this happens very fast, so by the time you sort it out, if you have forgotton to set the FCU up above your current altitude, you are so close in that the approach is unrecoverable and a go-around is the only option!

[felixthecat]

If there is one thing that history has taught us in aviation is that if it can go wrong sooner or later it will go wrong.

I have never flown the Bus and its not a Boeing SOP of which I am glad. An open decent close to the ground in a busy environment strikes me as something that can go wrong. We have backups in aviation to prevent isolated failures turning into catastrophes, I like using the automatics to back me up should I make a mistake….Of course that never happens though

Follow your SOPs they were written by people far cleverer than 90% of us gassing and moaning on here….just glad its not a Boeing SOP.

[HGVO]

Where is the problem? GS is still armed, you descend with a rate of about 1500fpm in Conf 2 until you capture the GS again. Of course you still have to comply with stabilized approach criteria, so if you are still out of limits at lets say 1000ft AGL you simply go around...

[Intruder]

If the pilot does not set the attitude above present altitude, it is likely the a/c will Alt capture (& level out) before intercepting the G/S.
As soon as possible select the Go Around Altitude

From current company SOP. I can't see a problem or threat with it to be honest.

Clearly if the GS isn't captured by 1000', a go around will be uppermost in the crews' mind. If it isn't captured by 500', there is no argument or discussion: a go around will be flown.

As felix indicates, such an "open descent" with no altitude protection is a good prelude to flying it into the ground if you get distracted and the G/S does not capture. If you can't capture the G/S before 1000' (assuming IMC), you WANT the Altitude to capture if you haven't initiated the Go-Around yet! If you're VMC, you should be flying the airplane and using the V/S in flight director mode for guidance. Again, if you are not on a reasonable glidepath at 500', you WANT the altitude capture to show on the FD to alert you!

I don't know what the Airbus proecedure have as a preface to that procedure, but it is a bad set-up.

[Capn Bloggs]

macdo has given a clear explanation as to why the SOP is constructed as it is.

Not really. All he has done is explain the apparently poxy ALT* system and why the best thing is to spin the ALT SEL out of the way, hence the SOP. It'll work every time, until someone misses the GS and prangs short.

[felixthecat]

Its a hole in the "swiss cheese" model….it always works until the other holes line up….

" We haven't crashed yet" isn't a valid argument

[Microburst2002]

G/S armed is as safe as ALT armed.

But It is possible to fly V/S without ALT armed and forgetting to arm approach. also, it may happen that G/S signal is down.

One day I remember that we were capturing from above and then something smelled rotten, we realised G/S signal wasn't there! It was a VMC day and we noticed the problem, but in a busier IMC situation, who knows, only EGPWS could warn you of an inminent crash into terrain.

My conclusion is: use the recommended method, but d not capture glideslopes from above in high workload or low situation awarenwss situations due to whatever circumstances. If in IMC, extra monitoring is required.

[de facto]

The classic use of speedbrake is Intruder's scenario: capturing GS from on high. Set a controlled ROD (~1500ft) and wait for GS capture. Of course, you keep configuring as per normal - if speed reduction doesn't occur, pull out the speedbrakes. Selecting Level Change/FLCH/Open Desc is asking for very high, unknown rates of descent

Totally disagree.
VS is for low rate of descent in TMA during CDAs..
If you need to increase your rate of descent,(ie above glide slope)use LvL chg and adjust speed to get your desired rate of descent.
Now you have speed protection and you dont have to destroy that energy with your speedbrakes.

[Intruder]

G/S armed is as safe as ALT armed.

But It is possible to fly V/S without ALT armed and forgetting to arm approach. also, it may happen that G/S signal is down.

In the 744 there is not an "ALT armed" selection, but I will assume the concept is the same as setting a target altitude in the MCP.

You contradict yourself in the second sentence. Assuming the autopilot engaged (as in the OP's query), V/S WILL capture the target altitude when that altitude is approached. An insufficient rate of descent may preclude G/S capture, in which case the airplane will impact the runway at the selected RoD. A G/S failure or outage or other anomaly may allow an impact short of the runway.

[quote]One day I remember that we were capturing from above and then something smelled rotten, we realised G/S signal wasn't there! It was a VMC day and we noticed the problem, but in a busier IMC situation, who knows, only EGPWS could warn you of an inminent crash into terrain.

My conclusion is: use the recommended method, but d not capture glideslopes from above in high workload or low situation awarenwss situations due to whatever circumstances. If in IMC, extra monitoring is required./quote]
The problem with that analysis is that it is EXACTLY the "high workload or low situation awarenwss situations" where a pilot might [blindly] choose to roll the V/S wheel down and the altitude wheel up, removing the protections when they are most needed.

If you are worried about a premature capture of the target altitude interrupting a reasonable intercept, then use the ILS minimums as the target, rather than the otherwise suggested 1000 or 500'. At least then you will be within go-around parameters when the altitude is captured.

[i_like_tea]

I think the problem with everyones above suggestions of how we "should" do our intercept from above procedure in the Airbus is just that.. it's how they think we should. How nice it would be if we were all at freedom to create our own SOPs... we're not, Airbus and the company want the altitude to be set above for a reason, and this is why we do and will continue to do it.

[felixthecat]

I disagree, we pointed out where we think the SOP could be a little lacking in our opinions and in fact in my last post I said that your SOP should be followed since its written by people cleverer than we are…I have an opinion thats all

[MD83FO]

I avoid using speedbrake to the maximum. The buffet is uncomfortable and they usually reveal poor descent planning.
On the 320 the managed descent usually leaves me below profile
I like to use VS mode, It is more comfortable, if im confronted with having to reduce speed i activate the approach phase getting rid of the speed bug or simply select a lower speed so i dont have to worry about the thrust increasing,
I control the speed with a combination of VS and speedbrake if required.
If above profile i press EXP DES down to 5000 if required ATC permiting. The extra drag from high speed descent really helps to capture the profile.

[macdo]

Just to add,
use of the Expedite button is banned in our airline and many others due to inadvertent loss of controlled flight. Lack of proper monitoring, probably.
I believe the function is removed or blanked on the later 320 models and on others it is replaced with the ALT button, which simply levels the aircraft off.

[zerozero]

That's hilarious.

They should rename the button then...

Something like:

A/C CNTRL

Crew can select ON or OFF.

[macdo]

Yes, its the French sense of humour.