Ask The Pilot

[Boris spatsky]

This video has sparked some questions from me:
1. What, if any, is the difference between wind sheer and a strong cross wind? Is wind sheer intermittent/lees predictable and cross wind more contstant?
2. Is the incident wind sheer or something else not evident from the video?
3. In a go around, how quickly might you typically raise the gear and reconfigure? The gear appears to be left down longer than for a standard departure. Is that typical for a go around? Is the delay likely just the crew attending to other tasks associzted with the go around, or could there be another reason(s?
4. Are there circumstances in a go around in which you might leave the gear down?

The reported wind was only 13 knots crosswind which is not an indicator of the prevalence windshear but the wind noise in the video makes me think that is inaccurate. It is also hard to tell how much crosswind there was as the video does not show the runway orientation.

The 737 landing technique is to keep the drift in (ie crab) until the flare, then apply rudder to align with the runway. As you do this you need to apply into wind aileron or the aircraft drifts downwind (and potentially off the side of the runway).

From watching the video, it appears that the initial rudder application had some associated downwind aileron input (or gust of wind) that dropped the downwind wing - the pilot overcompensated with upwind aileron and ended up with a wing strike (or fairing strike) and decided to go around.

The go around looks fairly normal rather than a windshear escape to me - in a windshear escape you leave the gear down and flaps and don't change the configuration until clear of the windshear. In this case if there wasn't shear, they may have thought that there was some gear damage or wing damage from the aborted landing and were being cautious, or just delayed the gear retraction by accident. Normally in the go around, the gear is retracted once a rate of climb and increase in altitude is called by the non flying pilot (called 'positive rate').

Crosswind is just wind component from across the runway - windshear is difference in windspeed and/or direction over a short distance. Windshear can lead to major airspeed fluctuations (loss or gain of airspeed), increase or decrease in rate of descent, significant changes in power required (increase or decrease) and significant turbulence.

Windshear is very unpredictable - it can be forecast but most times ATC tell you about it on the ATIS or from other pilot reports. Crosswind is very predictable, although gusty conditions less so.

 

[jb747]

3. In a go around, how quickly might you typically raise the gear and reconfigure? The gear appears to be left down longer than for a standard departure. Is that typical for a go around? Is the delay likely just the crew attending to other tasks associzted with the go around, or could there be another reason(s?

In this instance they appear to have had wing/pod strikes, possibly coupled with a heavy landing, with drift, on one oleo. Leaving everything hanging in the breeze might not be a bad idea, as you don't really know if it will come down again if you retract it.

4. Are there circumstances in a go around in which you might leave the gear down?

Quite a few. In windshear escape manoeuvres the configuration is not changed until the shear is no longer a factor. The overall drag of the aircraft increases during gear retraction, and if you are already on the performance limits you won't be able to afford that.

Any go around precipitated by a landing gear malfunction will have the gear being left down. The checklist may subsequently have you retracting it, but you don't want to do so if there's a chance of making things worse. Leave it until a checklist or ECAM calls for it.

 

[Saab34]

That QF video is not from today.

R34 arrival and the Sun is going down. The video was posted late morning.

 

[jb747]

That QF video is not from today.

R34 arrival and the Sun is going down. The video was posted late morning.

Apparently from a year or so ago. Looks similar to the Prague video, which is probably why it suddenly appeared.

 

[straitman]

I think there's even some Macchi recall items still rattling away in my head.

Other than a few rides on Instructors Course in 1977 it's about 45 years since I flew a Macchi and some bits still stick there....

Downwind checks:-
Speed below 150,
Speed brake in,
Undercarriage down etc

 

[jb747]

Other than a few rides on Instructors Course in 1977 it's about 45 years since I flew a Macchi and some bits still stick there....

Downwind checks:-
Speed below 150,
Speed brake in,
Undercarriage down etc

Speed below 150
Speed brake in
Landing gear down
3 wheels, flasher out
Hydraulics have recovered
Approach speed....

Now where is that wallet?

 

[jb747]

From another thread, with regard to the weather in Melbourne yesterday.

JB is Vr increased when operating in this type of weather to provide some sort of buffer against change of widespeed/direction during the takeoff roll?

Windshear on departure is handled by....choosing another runway, delaying/not going, using full power only (no derating allowed). An abort as a response to unacceptable speed variation on the take off roll is quite possible, even likely. The real answer is to not go!

The take off performance applications are somewhat cryptic in the way they vary their results as you change the input conditions. Basically, they can vary more of the factors than we did when using charted data, so numbers don't necessarily relate as you might expect. That means the answers are better, but it also requires a little more thought to ensure that you're happy with them. We'll choose the worst (most tail) wind component for departure calculations.

Using 34 (and some heavy, but not overly so 380 numbers):
Using a 0 knot headwind component (we can input the actual wind (direction and strength) or just a component value). We use both, but pick a worst case wind...the most adverse. Power, V1, Vr, V2, configuration.

Changing just dry or wet... gives a very small change.
Dry: Flex 37, 130, 154, 159, flap 2 Wet: Flex 36, 130, 153, 159, flap 2

Wet, 15 kt headwind component: Flex 39, 137, 161, 167, flap 1
Wet, 15 kt tailwind component: TOGA, 125, 147, 154, flap 3

So, you can see that all sorts of things are being changed with regard to speeds and configuration and power in response to changes in the conditions.

At the approach end of the runway, with windshear being reported, we may change the configuration to use less flap for the landing. The target IAS can also be adjusted upwards by up to 15 knots. Increasing the speed by more than a small value has its own issues. The pitch attitude will be reducing by about a degree for every 10 knots, and the aircraft will be much more inclined to float. The aircraft itself will vary the current speed target as it looks at the difference between the wind currently being experienced, and the wind loaded into the approach performance page of the FMC (the ATIS wind).

 

[Quickstatus]

From the Singair Delays thread:

To be honest, it strikes me as even worse if it was a 747 F, as they don't have tail skids.

Found a checklist. Here for those interested...http://www.737ng.co.uk/B777 QRH Quick reference Handbook.pdf

This is the leading line....
Do not pressurize the airplane.Pressurizing the airplane may cause
further structural damage.

I wonder if the ATC reported the possible tailstrike to the SQ pilots causing a necessary return to base as presurrised flight would/could be dangerous.

Or does the B777 have tail strike indicators or protection systems in the flight computer warning of incorrect geometry during rotation?

 

[jb747]

I wonder if the ATC reported the possible tailstrike to the SQ pilots causing a necessary return to base as presurrised flight would/could be dangerous.

ATC would report that they saw a tail strike. It isn't up to them to make inputs beyond that. They'd then have sent out the safety vehicles for a runway inspection. A tail strike wouldn't necessarily be all that obvious. I've seen the aftermath of some very serious ones, and the runways aren't necessarily heavily marked.

Or does the B777 have tail strike indicators or protection systems in the flight computer warning of incorrect geometry during rotation?

I expect that it has some form of pitch limit display during rotation, but I don't know for sure. We have a 777 pilot here, and he might give us an answer to that. The A380 shows a tail strike limit on the PFD during rotation.

There is an EICAS warning associated with a strike, and that's what would trigger the warning for the checklist. The airmanship question is this...If ATC have seen the strike, but the EICAS isn't reporting it, is it sensible to ignore it?

 

[Quickstatus]

ATC would report that they saw a tail strike. It isn't up to them to make inputs beyond that. They'd then have sent out the safety vehicles for a runway inspection. A tail strike wouldn't necessarily be all that obvious. I've seen the aftermath of some very serious ones, and the runways aren't necessarily heavily marked.



I expect that it has some form of pitch limit display during rotation, but I don't know for sure. We have a 777 pilot here, and he might give us an answer to that. The A380 shows a tail strike limit on the PFD during rotation.

There is an EICAS warning associated with a strike, and that's what would trigger the warning for the checklist. The airmanship question is this...If ATC have seen the strike, but the EICAS isn't reporting it, is it sensible to ignore it?

When I was looking for a Cargo Flight tail strike with a SQC flight number and could not find it, I thought that maybe the aircraft did a return to base and was just not recorded anywhere.
Im surprised that confirmation of "no tail strike" seemed to have occurred only at the other end after an 8 hour pressurised flight.

Maybe pitch attitude was within normal parameters and so they discounted ATC, however 8 hours in a pressurised and possibly cracked metal tube is never a good idea.....Rather be down here wishing i was up there.....


But I wonder what prompted the pilots to continue?

 

[AviatorInsight]

From the Singair Delays thread:




I wonder if the ATC reported the possible tailstrike to the SQ pilots causing a necessary return to base as presurrised flight would/could be dangerous.

According to reports from The Australian, ATC did advise the crew of a possible tail strike and a runway inspection was carried out. No debris or markings were found. Having said that, reports from another forum indicate the aircraft did in fact sustain damage and is undergoing repairs now in SIN.

Or does the B777 have tail strike indicators or protection systems in the flight computer warning of incorrect geometry during rotation?

The B777 does indeed have pitch limit indicators on the PFD. These are displayed whenever the flaps are out of the UP position. However, that's not primarily used for tail strike avoidance, more so for protection from the stall.

If the tailskid did in fact make contact with the runway, an EICAS message would appear with an associated checklist, and advise the crew to depressurise the aircraft and plan to land at the nearest suitable airport.

The airmanship question is this...If ATC have seen the strike, but the EICAS isn't reporting it, is it sensible to ignore it?

From the manual (my bolding), "anytime fuselage contact is suspected or confirmed, accomplish the appropriate checklist without delay". I think that would definitely be enough for me to warrant a return (or in this case perhaps fly depressurised to an airport without 51kt winds).

 

[jb747]

The B777 does indeed have pitch limit indicators on the PFD. These are displayed whenever the flaps are out of the UP position. However, that's not primarily used for tail strike avoidance, more so for protection from the stall.

The PLIs or 'eyebrows'? Standard Boeing. The 380 is a specific tail strike limit.

From the manual (my bolding), "anytime fuselage contact is suspected or confirmed, accomplish the appropriate checklist without delay". I think that would definitely be enough for me to warrant a return (or in this case perhaps fly depressurised to an airport without 51kt winds).

Ah, airmanship. It's really a bit like commonsense...which is not common.

Often you wonder what drives some of the decisions that we see or hear about.

In the latest Dubai accident, the go around was apparently forced by a 'long landing' warning, which the pilots' SOP says must be followed. So, yes, the landing was long, but there was still 9,000 feet in front of them. SOP pushes them into something that goes wrong. SOPs are designed to ensure blame can't be sleeted home to management, not necessarily to ensure the safest things happen.

Number 2 at holding point one horrid night in HK, waiting to take off. Watched a freighter go. Decided I really didn't like it, so I decided to return to the gate. I had to enter the runway to do so, and as I was exiting, heard the freighter come back up and say "all aircraft waiting to go, DO NOT TAKE OFF". A ripple of radio calls from others deciding that following me back was a good idea. The usual suspects, one of whom had recently lost an aircraft in similar conditions, still took off.

Line up. Don't like what I can see on the radar. Say that I'm going to wait for a while. Go to parallel taxiway, where I'm joined by a number of other 747s. Again, a number of the usual suspects depart.

Starting up one night. Push back has me blocking access to a gate (which is quite normal). Idiots taxi between us and aircraft parked on next bay. Ends up at 45º to line up. Misses, I have no idea how, us, aircraft on other side, and the bridges. Can't unload anyway, as can't connect to anything. He'd have had to wait no more than a minute for us to taxi clear.

In this tail strike case, staying at lower level (10,000) and pointing at Adelaide would give time to assess properly, whilst closing in on a reasonable diversion field. Who knows, it might be like the engine fire warning that's stopped...because the engine has fallen off.

 

[docjames]

jb747, in a number of posts in this eternally fantastic thread, you've alluded to the "usually suspects" who've gone and taken off in weather you (and others) have chosen not to.

Is it possible to "discover" who chose to take off (so as I might avoid to flying them!)?

Or perhaps a kinder alternative, who else chose to wait?

 

[Quickstatus]

Currently SYD airport is under parallel runway operations. Can you discuss the pros and cons of parallel runway ops at SYD.

Runway 16L/R

I think the parallel runways are close together causing issues of aircraft separation.

 

[jb747]

jb747, in a number of posts in this eternally fantastic thread, you've alluded to the "usually suspects" who've gone and taken off in weather you (and others) have chosen not to.

Is it possible to "discover" who chose to take off (so as I might avoid to flying them!)?

Or perhaps a kinder alternative, who else chose to wait?

Let's see...no.

I'll be accused of being
a) Biased
b) Racist
c) Xenophobic

Most of the suspects are quite popular with AFF members, because (cross out as required)
a) they are good at service
b) very good at marketing
c) people have short memories
d) they're cheap
e) lightning doesn't strike twice
f) a river in Egypt

 

[JohnM]

Let's see...no.

I'll be accused of being
a) Biased
b) Racist
c) Xenophobic

Most of the suspects are quite popular with AFF members, because (cross out as required)
a) they are good at service
b) very good at marketing
c) people have short memories
d) they're cheap
e) lightning doesn't strike twice
f) a river in Egypt

Well played, suh!

 

[jb747]

Currently SYD airport is under parallel runway operations. Can you discuss the pros and cons of parallel runway ops at SYD.

Runway 16L/R

I think the parallel runways are close together causing issues of aircraft separation.

Thankfully Sydney is pretty much off my destination list these days.

Normally parallel runways are of similar length to each other, and at modern airports are designed so that one can be used for arrivals, and the other departures.

As an airport, Sydney was delivered by Noah. The configuration is appalling, with aircraft needing to cross runways for many operations, and dissimilar lengths meaning that the closest runway is often not operationally acceptable. Pressure is applied by ATC (and presumably they're pressured in turn) for aircraft to use runways that are marginal at best. Listening to the discussion with some of the foreign pilots is cringeworthy.

The the parallels are too close to allow normal simultaneous instrument approaches, which means a very poor system called PRM must be used to ensure separation in the event that someone drifts off their centreline. The slow downs caused by instrument approaches mean that ATC is always pushing aircraft to accept visual approaches.

 

[dajop]

jb747, I have a question .... how much, particularly in managing incidents, do you rely on laid out company procedures vs your own judgement, training and problem solving ability? Particularly the problem solving piece.

The reason I ask, having lived in Singapore for almost eight years, I have noticed that the educational approach here (and to be fair across much of this part of the world) is geared to rote learning and not solving problems. It is what it is. Furthermore the culture here is very rules/compliance focused - to the point that most (but certainly not all, there are many exceptions) people blindly follow rules and procedures without making any judgement of other data points. The moment something comes up that is outside the rules or pre-learning things easily go into meltdown, as problem solving does not come into it, and usually there is a "cannot" type response. I experience this regularly in the workplace. In an aviation context , I am not sure how this plays out, as I know SOPs (or whatever they are called in flight context) are important, but a deficiency in problem solving ability really worries me from the point of view of a passenger.

When I hear about things like an SQ pilot ignoring ATC observations and following just what instrumentation indicates (it must be right, surely), it is completely unsurprising to me. It would also not surprise me if a number of other airlines and pilots judged a situation to dangerous to take off, based on synthesising all available data and combine that with some experience, whereas pilots educated here might take a different approach, as long as their decision fits into parameters laid out then it is OK.

 

[docjames]

Let's see...no.

I'll be accused of being
a) Biased
b) Racist
c) Xenophobic

Most of the suspects are quite popular with AFF members, because (cross out as required)
a) they are good at service
b) very good at marketing
c) people have short memories
d) they're cheap
e) lightning doesn't strike twice
f) a river in Egypt

Disappointing (but understandable).

Guess i'll have to take my chances (and hope i don't choose based on the above).

 

[AviatorInsight]

Currently SYD airport is under parallel runway operations. Can you discuss the pros and cons of parallel runway ops at SYD.

Runway 16L/R

I think the parallel runways are close together causing issues of aircraft separation.

As JB mentioned above, a real Con I can see as well would be the use of the PRM approaches during poor weather (and also during good weather as a result of ATC currency). The downwind leg always get lengthened and is a limitation of the narrow distance between the two runways (1037m apart).

However, parallel runways would have been put into the airport plan as a result of capacity. Allowing aircraft to arrive and depart at the same time. It also allows the spread for noise abatement (using SODPROPS for example).