Ask The Pilot

[Major]

and wave the pin with red flag attached for you to acknowledge ?

 

[AviatorInsight]

Interesting thread. I work for the Bureau of Meteorology. I'm curious how useful our services are to pilots?

A lot of the time we will look at the weather and make our own judgements and predictions, especially coming into fog season and no fog has been forecast. This usually comes from having flown into a number of ports using past experience.

I actually use a number of your services from the website to get an overall picture of the day's flying, SIGWX High/Low, satellite photos, current SIGMETs or wind shear warnings, etc. Putting that together with the weather we get from the company (GRIB winds for the route) and I can usually get a good idea of what it'll look like. This is particularly helpful coming into winter with strong jet streams causing a few overspeeds on the climbs and descents.

 

[AviatorInsight]

As a passenger you notice typical sequences.
Recently on 2 TAP A332 flights it seemed a bit different.
#1 was at Boston, where the engines were powered up at the gate and run for 10 minutes before push back.
#2 was on approach to Newark. After a normal descent, we were held at maybe 6000ft for a number of minutes doing a zigzag before lining up. The undercarriage went down, and it was only then that the flaps were applied, all the way in one go, and we landed a couple of minutes later.

Do either of those seem unusual ?

Not knowing Airbus and having never been to Boston or Newark, both of those still seem unusual. In the first instance, having an unserviceable APU and requiring to start one on the gate I can understand, but starting both before a pushback?

In the second instance, using the gear before any flap indicates that they were very fast. The zig zagging is typical of needing extra track miles to compensate for getting high. Once the speed starts reducing from the large amount of drag from the gear then you can start taking flap out. To take it out all in one hit would have caused a massive ballooning effect. I suspect it was still taken in stages let the speed stabilise (even if only for a brief second) then bringing the rest of them out.

 

[ayebee]

Not knowing Airbus and having never been to Boston or Newark, both of those still seem unusual. In the first instance, having an unserviceable APU and requiring to start one on the gate I can understand, but starting both before a pushback?

In the second instance, using the gear before any flap indicates that they were very fast. The zig zagging is typical of needing extra track miles to compensate for getting high. Once the speed starts reducing from the large amount of drag from the gear then you can start taking flap out. To take it out all in one hit would have caused a massive ballooning effect. I suspect it was still taken in stages let the speed stabilise (even if only for a brief second) then bringing the rest of them out.

Thanks.

re #1, I had a window on right rear of the wing and I know the engine on my side was running. On reflection, I can't be sure if the left engine was also running, so your thoughts on APU could explain it.

re #2. If you are interested the track ... Live Flight Tracker - Real-Time Flight Tracker Map | Flightradar24
Coming into the NY airports always seems to involve some turns away and back. The track out and back over NJ felt like level flight for about 10 minutes. Other than the gear / flaps sequence, the actual landing seemed normal.

 

[jb747]

As a passenger you notice typical sequences.
Recently on 2 TAP A332 flights it seemed a bit different.
#1 was at Boston, where the engines were powered up at the gate and run for 10 minutes before push back.
#2 was on approach to Newark. After a normal descent, we were held at maybe 6000ft for a number of minutes doing a zigzag before lining up. The undercarriage went down, and it was only then that the flaps were applied, all the way in one go, and we landed a couple of minutes later.

Do either of those seem unusual ?

Not particularly.

The exact sequence for an engine start can be affected by many things. East coast USA in particular, is very busy, and getting things out of the way, so that they aren’t done sitting on, and blocking, a taxiway may be useful.

It was quite common flying into JFK to be descended quite early, and to then do a tour of the state at a few thousand feet. Not very efficient from our point of view, but given the multiplicity of airports in close proximity, with approach and departure paths winding through each other, not surprising. Added to that is the general US controller habit of getting aircraft to maintain higher than usual speeds (and then being quite narky if you tell them you want to slow) and you can often end up with more energy than you ideally want at any given point on the approach. The landing gear is a very effective speed brake. If you look at QF93 and 11 arrivals into LA, the gear is often taken very early on right base, and is often out of ‘sequence’. You simply need extra drag, and the gear provides lots of it. At the 200 knots or so that you’re doing at that point, the speed brakes are relatively ineffective.

The flaps would not have been selected in one hit. Each stage would have been selected below its limiting speed. So, whilst the selection would have been 1, 2, 3, full, with a gap between each selection, they don’t instantly arrive at each position, so the actual run could have been more or less continuous.

 

[woodborer]

Not knowing Airbus and having never been to Boston or Newark, both of those still seem unusual. In the first instance, having an unserviceable APU and requiring to start one on the gate I can understand, but starting both before a pushback?

I've been on a Qantas A330 where they fired up an engine before pushback due apparently to some maintenance that had just been performed on it.

 

[AviatorInsight]

I've been on a Qantas A330 where they fired up an engine before pushback due apparently to some maintenance that had just been performed on it.

I actually had to start one on the bay last week for an entire day due to unserviceable APU so that in itself is of no surprise, but to start both before pushing back is something I hadn’t seen or done.

 

[woodborer]

I actually had to start one on the bay last week for an entire day due to unserviceable APU so that in itself is of no surprise, but to start both before pushing back is something I hadn’t seen or done.

Yep, pretty sure it was only one of them...I'm sure the captain said which one but I only registered it as something different, so don't remember which.

 

[jb747]

I've been on a Qantas A330 where they fired up an engine before pushback due apparently to some maintenance that had just been performed on it.

Sometimes a maintenance job isn’t complete until the engine is run for a while. There are quite a few variations to that theme. The engine might just need to be run. It might need the cowls to be reopened after running for few minutes and then shutting down. Whilst it’s nice to have all of that done before boarding, sometimes it just doesn’t work out that way.

When the APU is missing in action, on the twins, starting a single engine on the bay, will give you half of the normal electrical supply, and is normally sufficient to disconnect external power and push. On the quads, that’s only 25% of normal, and whilst you can push back like that, you’ll need to shed quite a lot of the load, by selecting lots of items off. There’s a checklist for that, but it’s much easier if you can start a second engine before pushing. On the 380 it doesn’t really matter which pair, but we’d prefer one on each side.

 

[ayebee]

Not particularly.

The exact sequence for an engine start can be affected by many things. East coast USA in particular, is very busy, and getting things out of the way, so that they aren’t done sitting on, and blocking, a taxiway may be useful.

It was quite common flying into JFK to be descended quite early, and to then do a tour of the state at a few thousand feet. Not very efficient from our point of view, but given the multiplicity of airports in close proximity, with approach and departure paths winding through each other, not surprising. Added to that is the general US controller habit of getting aircraft to maintain higher than usual speeds (and then being quite narky if you tell them you want to slow) and you can often end up with more energy than you ideally want at any given point on the approach. The landing gear is a very effective speed brake. If you look at QF93 and 11 arrivals into LA, the gear is often taken very early on right base, and is often out of ‘sequence’. You simply need extra drag, and the gear provides lots of it. At the 200 knots or so that you’re doing at that point, the speed brakes are relatively ineffective.

The flaps would not have been selected in one hit. Each stage would have been selected below its limiting speed. So, whilst the selection would have been 1, 2, 3, full, with a gap between each selection, they don’t instantly arrive at each position, so the actual run could have been more or less continuous.

Thanks.
I can relate to the "tours" over NY, NJ and the Atlantic.

 

[Major]

How quickly does the aircraft react to your correctional inputs on very windy days ?

 

[AviatorInsight]

How quickly does the aircraft react to your correctional inputs on very windy days ?

The 737, very quickly. Controls are still directly linked to the control surfaces. So on windy days I don’t need to go to the gym.

 

[jb747]

How quickly does the aircraft react to your correctional inputs on very windy days ?

The answer is very quickly...but there is a difference across aircraft types. Basically the bigger the aircraft, the slower the response.

There are a couple of separate issues at play. Engine response is almost instant, as long as the power isn't coming off idle, when there can be a couple of seconds delay. Pitch response nose down is very rapid, but getting rid of any established sink rate is a slower exercise...so it's not just the change in attitude that you need, but also time for the various vectors to have an effect.

Roll response tends to have a tiny delay, which varies with the length and flexibility of the wing. Basically, you put an input in, and the wing bends a little and then rolls the aircraft. One effect of this is the very noticeably over controlling in roll that is often evident on youtube videos. You need to be doubly careful about this in Airbus, as the aircraft itself will attempt to correct any roll disturbances...you need to learn to slow your inputs to give it a chance.

When I first came to the airline, I found the roll response of the 747 to be glacial, but then I was coming from an aircraft with a roll rate about 30 (!) times greater. The 767 was noticeably faster, and then back to the 747 where, for a time at least, it was annoyingly slower. The 380 was at least as fast as the 747, but with the added proviso of trying not to get into a fight with the FBW. That actually takes a couple of years (or more) to learn.

 

[Quickstatus]

The 737, very quickly. Controls are still directly linked to the control surfaces. So on windy days I don’t need to go to the gym.

A car has power steering which augments steering Inputs.

Presumably non FBW aircraft like the 737 have a certain degree of non power assisted mechanical advantage engineered into the controls to allow a pilot to change the aircraft’s attitude. But is there also power assistance (hydraulic or electrical actuators) that assists that pilot input?.

 

[jb747]

A car has power steering which augments steering Inputs.

Presumably non FBW aircraft like the 737 have a certain degree of non power assisted mechanical advantage engineered into the controls to allow a pilot to change the aircraft’s attitude. But is there also power assistance (hydraulic or electrical actuators) that assists that pilot input?.

And aircraft are very much the same.

As far as I know, none of the airliners have any form of manual control. I doubt that you’d have any chance of even slightly moving the controls without hydraulic assistance. The last aircraft that I flew that was fully manual was the Macchi. The A4 had hydraulically actuated flight controls, but with a manual reversion. Flight in manual was so difficult that it was generally just done the once on conversion, and then you crossed your fingers and hoped never to see it again.

 

[AviatorInsight]

A car has power steering which augments steering Inputs.

Presumably non FBW aircraft like the 737 have a certain degree of non power assisted mechanical advantage engineered into the controls to allow a pilot to change the aircraft’s attitude. But is there also power assistance (hydraulic or electrical actuators) that assists that pilot input?.

Correct. So the cables are mechanically linked to hydraulic power control units when everything is working well. Start losing hydraulic pressure and it’s known as a manual reversion. Very hard to control and very heavy as there’s a massive null zone in the control column around the neutral position.

 

[opusman]

Have any pilots here ever had any attempted stowaways?

 

[AviatorInsight]

Have any pilots here ever had any attempted stowaways?

Never.

 

[lastrow]

How is beating between two engines controlled? Is it a matter of fine tuning throttle settings or is it automatic. Sitting in the back of a rear engined aircraft during takeoff is bad enough but when the engines beat against each other the effect is horrific.

 

[AviatorInsight]

How is beating between two engines controlled? Is it a matter of fine tuning throttle settings or is it automatic. Sitting in the back of a rear engined aircraft during takeoff is bad enough but when the engines beat against each other the effect is horrific.

Usually with the autothrottle engaged it’ll sort itself out. The only time would really be on descent when the thrust mode goes to ‘arm’ and then the PF adds thrust manually for various reasons. It’ll be then as the thrust comes up that there may be an out of sync noise with the engines heard until they match them up again.

I haven’t sat in the back of a rear engined aircraft enough to really take notice. The pistons are notorious for it and used to really irk me when students wouldn’t sync up the props.