Ask The Pilot

[moa999]

What should you do if you see a UAV close to an active approach?

https://www.casa.gov.au/webform/unsafe-drone-operations-complaint-form

Or the local constabulary. Sharp word from the right person may have a better effect.

 

[jb747]

........

Essentially, if the crew was available and passengers too, and there were no other constraints such as the SYD curfew at the other end, would a flight like this that isn't in the timetable during the 'restricted' hours be allowed to depart?

Unless it was part of a general delay affecting Heathrow, I'd not expect such a turnaround to be approved.

 

[jb747]

What should you do if you see a UAV close to an active approach?

I live very near the end of RWY11 at DRW. Tonight I saw someone who lives nearby fly a drone very close to the approach. I estimate it was operating between 0 and 500ft and around 700m north of the extended centreline. Certainly within 5nm of the field.

A quick google for a phone number to the TWR turned up nothing. Not surprising really, because I guess they don't want it to become a noise complaint hotline and or have a stream of pranksters.

I also couldn't find anything useful on the Air Services page. And of course DRW is Defence operated anyway.

I'm not entirely comfortable knocking on the bloke's door.

Suggestions?

Tell local police. Report it to CASA.

I think the limit is actually 5 km...though I'm certainly no drone expert. Some operators do have approvals to operate at airfields.

 

[jb747]

If you had two aircraft of the same type, one being serviced in the US and one in Australia, how similar are the maintenance plans?

I'd expect them to be identical. Such plans are generated by the manufacturers.

 

[Quickstatus]

Re "Super" aircraft wake turbulence

Accident: Emirates A388 over Arabian Sea on Jan 7th 2017, wake turbulence sends business jet in uncontrolled descent

Are there company specific/ ATC recomendations regarding separation from "Super" aircraft to minimise wake turbulence?. Are they adequate?

 

[AviatorInsight]

Re "Super" aircraft wake turbulence

Accident: Emirates A388 over Arabian Sea on Jan 7th 2017, wake turbulence sends business jet in uncontrolled descent

Are there company specific/ ATC recomendations regarding separation from "Super" aircraft to minimise wake turbulence?. Are they adequate?

In RVSM (Reduced Vertical Separation Minima) Airspace, no there is no minimum separation from "Super" to other categories. It's the standard 1000ft separation that will apply to all aircraft. However, you do need to be smart about it. When we are following a super in the cruise (depending on the wind of course) but the wake will generally drift down at 500fpm.

Due to today's accuracy of GPS flying, (it's actually scary how accurate these things are), we will be following directly behind the preceding aircraft. In RVSM airspace we are allowed a 2nm offset to the RIGHT only without a clearance for such instances. We regularly use this when flying on airways to minimise the wake off other aircraft.

Take off and landings however, certain minimum separation standards apply between the different categories of aircraft.

 

[jb747]

Re "Super" aircraft wake turbulence

Accident: Emirates A388 over Arabian Sea on Jan 7th 2017, wake turbulence sends business jet in uncontrolled descent

Are there company specific/ ATC recomendations regarding separation from "Super" aircraft to minimise wake turbulence?. Are they adequate?

From my point of view, wake turbulence isn't much more than a momentary inconvenience. The 380 creates plenty, but it also isn't dramatically affected by it (certainly well within the control authority).

Travelling from Sydney in a 737 a couple of years back, the 737 was literally in the cone of a preceding 747's wake, and it was rolling a surprising, and uncomfortable, amount. The crew quickly fixed it with an offset.

Because the wake descends, if you follow exactly the vertical and lateral path of another aircraft, it will normally be thump free, which is probably why it isn't an issue for most arrivals.

I would really expect the biz jet people to be aware of, and proactive in their avoidance of, heavy jet wake. Worth noting too, that the worst wake of all came from the 757...it could give a 747 a decent thump.

 

[Quickstatus]

relatively inefficient ? More wake turbulence?

 

[Caversham04]

In the comments on AusBT's recent article on TAP's new (fully-flat) A330-900 business class, a reader notes that "the seat does not look remotely flat" [meaning in this instance that the seat is flat but is NOT horizontal / parallel to the floor of the cabin]. Someone else has replied that "fully flat airline seats are angled slightly because an airplane is always angled slightly upwards during travel" [i.e. even when travelling at constant altitude]. I've also consistently noticed a slight nose-up attitude when flying on wide-body jets (less so on a 737 / A320). There will obviously be a good reason for it, but it seems counter-intuitive as surely this would cause higher drag than if the airflow was perfectly parallel to the long axis of the airplane? Can anyone shed some light on this, please?

 

[tgh]

In the comments on AusBT's recent article on TAP's new (fully-flat) A330-900 business class, a reader notes that "the seat does not look remotely flat" [meaning in this instance that the seat is flat but is NOT horizontal / parallel to the floor of the cabin]. Someone else has replied that "fully flat airline seats are angled slightly because an airplane is always angled slightly upwards during travel" [i.e. even when travelling at constant altitude]. I've also consistently noticed a slight nose-up attitude when flying on wide-body jets (less so on a 737 / A320). There will obviously be a good reason for it, but it seems counter-intuitive as surely this would cause higher drag than if the airflow was perfectly parallel to the long axis of the airplane? Can anyone shed some light on this, please?

I will take a punt and cheerfully accept correction from a "real" pilot.
The fuselage acts as an aerofoil and to create lift must run at a positive angle of attack.. aka sloping upwards
Having said that mouthful can't say I have ever noticed ..

 

[AviatorInsight]

In the comments on AusBT's recent article on TAP's new (fully-flat) A330-900 business class, a reader notes that "the seat does not look remotely flat" [meaning in this instance that the seat is flat but is NOT horizontal / parallel to the floor of the cabin]. Someone else has replied that "fully flat airline seats are angled slightly because an airplane is always angled slightly upwards during travel" [i.e. even when travelling at constant altitude]. I've also consistently noticed a slight nose-up attitude when flying on wide-body jets (less so on a 737 / A320). There will obviously be a good reason for it, but it seems counter-intuitive as surely this would cause higher drag than if the airflow was perfectly parallel to the long axis of the airplane? Can anyone shed some light on this, please?

A great question!

It actually has to do with the best lift:drag ratio. As the name implies, it is the amount of lift generated by a wing or aerorfoil compared to its drag. A ratio of L/D indicates aerofoil efficiency. Aircraft with higher L/D ratios are more efficient than those with lower L/D ratios.

Because of the relationship between the wing, the shape of it, and how that produces lift, the maximum L/D ratio occurs at one specific AoA (Angle of Attack). If the aircraft is operated in steady flight at the L/D max ratio, then total drag is at a minimum. Any AoA lower or higher than that producing the maximum L/D ratio reduces it and consequently increases the total drag for a given aircraft's lift.

Having said all that, the B777 will operate at around 2.5º nose up in the cruise. So when the beds are laid flat they are angled slightly down to compensate for this nose up attitude and is then seen as being 'flat'.

 

[AviatorInsight]

I will take a punt and cheerfully accept correction from a "real" pilot.
The fuselage acts as an aerofoil and to create lift must run at a positive angle of attack.. aka sloping upwards
Having said that mouthful can't say I have ever noticed ..

That's pretty close for a punt! But yes, at 2.5º, it's not that noticeable, but if I go for a walk to the back of the aircraft, I can definitely sense that there's a slight angle going on there.

 

[Caversham04]

A great question!

It actually has to do with the best lift:drag ratio. As the name implies, it is the amount of lift generated by a wing or aerorfoil compared to its drag. A ratio of L/D indicates aerofoil efficiency. Aircraft with higher L/D ratios are more efficient than those with lower L/D ratios.

Because of the relationship between the wing, the shape of it, and how that produces lift, the maximum L/D ratio occurs at one specific AoA (Angle of Attack). If the aircraft is operated in steady flight at the L/D max ratio, then total drag is at a minimum. Any AoA lower or higher than that producing the maximum L/D ratio reduces it and consequently increases the total drag for a given aircraft's lift.

Having said all that, the B777 will operate at around 2.5º nose up in the cruise. So when the beds are laid flat they are angled slightly down to compensate for this nose up attitude and is then seen as being 'flat'.

View attachment 93632

Many thanks for the rapid reply. It all seems to be driven by the wing (and its optimum AoA), which seems reasonable to a layman...... but why wouldn't you attach the wing to the fuselage such that in the cruise, the wing is at the optimum AoA (for maximised L/D ratio) while the fuselage is perfectly parallel to the airflow (rather than, for example, the 2.5º nose up attitude for a B777)? As a layman, I would be aiming to minimise the drag caused by the fuselage by presenting the minimum cross-sectional area to the airflow, plus the fuselage is (presumably) optimally streamlined from directly front-on? I guess it could be a compromise associated with take-off and climb and / or descent and landing? I guess it also becomes more important for larger aircraft as they'll be at cruising altitude for longer......?

 

[Caversham04]

That's pretty close for a punt! But yes, at 2.5º, it's not that noticeable, but if I go for a walk to the back of the aircraft, I can definitely sense that there's a slight angle going on there.

Sorry - have just seen this after typing my initial reply to Aviator Insight's explanation.......

Is the lift created by presenting the fuselage at 2.5º to the airflow significant, relative to the lift provided by the wings, and what is the increase in drag caused by pushing the fuselage through the air at a nose-up angle as opposed to horizontally, when presumably the streamlining is most effective?

 

[AviatorInsight]

Many thanks for the rapid reply. It all seems to be driven by the wing (and its optimum AoA), which seems reasonable to a layman...... but why wouldn't you attach the wing to the fuselage such that in the cruise, the wing is at the optimum AoA (for maximised L/D ratio) while the fuselage is perfectly parallel to the airflow (rather than, for example, the 2.5º nose up attitude for a B777)? As a layman, I would be aiming to minimise the drag caused by the fuselage by presenting the minimum cross-sectional area to the airflow, plus the fuselage is (presumably) optimally streamlined from directly front-on? I guess it could be a compromise associated with take-off and climb and / or descent and landing? I guess it also becomes more important for larger aircraft as they'll be at cruising altitude for longer......?

I see what you're trying to get at, but the fuselage doesn't generate that much lift or create that much drag in the big scheme of things. To keep it simple, there needs to be a compromise to the angle that the wing is attached to the fuselage to still be able to produce enough lift at all phases of flight and not require as much thrust thereby increasing the amount of fuel required.

In level flight our flight path vector (angle) is 0º with a pitch attitude of 2.5º. This is what gives us our best lift:drag ratio. As the fuel burns off our flight path angle is still 0º but our pitch attitude may now be 2º.

This pic I found below explains it well.

 

[Caversham04]

I see what you're trying to get at, but the fuselage doesn't generate that much lift or create that much drag in the big scheme of things. To keep it simple, there needs to be a compromise to the angle that the wing is attached to the fuselage to still be able to produce enough lift at all phases of flight and not require as much thrust thereby increasing the amount of fuel required.

In level flight our flight path vector (angle) is 0º with a pitch attitude of 2.5º. This is what gives us our best lift:drag ratio. As the fuel burns off our flight path angle is still 0º but our pitch attitude may now be 2º.

Thank you for the extra information - in summary, if I've understood it correctly, it's a "whole-of-flight" calculation and the very minor fuselage-drag penalty associated with a slight and constant upwards pitch during cruise is outweighed due to savings related to greater efficiency during climb and descent?

 

[AviatorInsight]

Thank you for the extra information - in summary, if I've understood it correctly, it's a "whole-of-flight" calculation and the very minor fuselage-drag penalty associated with a slight and constant upwards pitch during cruise is outweighed due to savings related to greater efficiency during climb and descent?

Basically, yes. The best L/D ratio is set up for the cruise. During climb there's not much you can save there, and during descent we are at idle thrust usually, to maximise the fuel saving potential there.

I'm sure there will be others who have a slightly different viewpoint (understanding?) to me that will be able to delve a little deeper into the subject. That's about my extent without going into lift equations.

 

[jb747]

..... but why wouldn't you attach the wing to the fuselage such that in the cruise, the wing is at the optimum AoA (for maximised L/D ratio) while the fuselage is perfectly parallel to the airflow (rather than, for example, the 2.5º nose up attitude for a B777)?

If you have a look here: https://en.wikipedia.org/wiki/Vought_F-8_Crusader you find information on a lovely aircraft that actually made use of variable incidence. Basically they changed the rigging angle for low speed operations.

I think you'll find that the most limiting factor to the rigging angle on an airliner relates to gear down operations near the ground. It would be difficult to get the slightly negative angle of attack you want when on the ground. The aircraft would be trying to lift off before normal rotation. It would also make the pitch angle on approach approximately zero, which would dramatically increase the likelihood of nose gear first landings.

It's a trade off. Slightly more drag versus undesirable geometry gear down.

 

[Caversham04]

Basically, yes. The best L/D ratio is set up for the cruise. During climb there's not much you can save there, and during descent we are at idle thrust usually, to maximise the fuel saving potential there.

I'm sure there will be others who have a slightly different viewpoint (understanding?) to me that will be able to delve a little deeper into the subject. That's about my extent without going into lift equations.

Many thanks again for the explanation / insight!

 

[flychrisfly]

Due to today's accuracy of GPS flying, (it's actually scary how accurate these things are), we will be following directly behind the preceding aircraft. In RVSM airspace we are allowed a 2nm offset to the RIGHT only without a clearance for such instances. We regularly use this when flying on airways to minimise the wake off other aircraft.

How accurate is GPS in terms of vertical separation? Given every measurement/measuring device is subject to a degree of error, how close would 2 planes likely come if they were travelling at '1000ft vertical separation'?