Ask The Pilot

[Major]

I assume that relates to the QF29 VH-OJU stick shaker report. Thread in Open Discussion

There is some detail here

Accident: Qantas B744 near Hong Kong on Apr 7th 2017, stick shaker activation in holding pattern injures 15 passengers

 

[Captain Halliday]

How common is turbulence as a cause of a stick shaker activation?

I assume that relates to the QF29 VH-OJU stick shaker report. Thread in Open Discussion

It does. However, there is quite a lot of speculation in that thread, so I posed my question here hoping for an answer from one of our pilot contributors without the emotion and hyperbole.

 

[yohy?!]

And how much attitude would they have lost to injure 15 when the pilot pushed the stick forward to prevent a stall?

 

[AviatorInsight]

Watched a video on how aircraft fly ten dynamic routes between Europe and North America.

Canadian air services publish the changing routes daily, the idea behind these routes is to counter no radar, aircraft also work with increased separation

Does this concept exist over the pacific?

Like por930 mentioned the PACOTS system, from Australia to the US we can use a system known as a UPR (User Preferred Route). Basically this system allows us to fly the most economic routing (from our flight planning department) and doesn't necessarily follow a published airway.

 

[AviatorInsight]

How common is turbulence as a cause of a stick shaker activation?

Up at altitude where the margin between stick shaker and overspeed is small (known as coffin corner), turbulence can most definitely be a factor. Down at 20,000ft where the margin is greater, not so much. That is not to say it's not possible though. As with any incident/accident there are a lot of variables. What was the holding speed? Was it ATC related or aircraft related? Were there icing conditions present? Was the aircraft in a clean or dirty configuration? Was it turning when it happened (this increases the amount of lift required)?

I'm sure there are lots more questions to be asked, but like others have quite correctly stated on the other thread, it is a reaction to an impending stall. The aircraft has not at this point stalled. The vibration they would have felt would have been the buffeting from the disrupted airflow over the tailplane. The pilots did a great job and stopped the situation from getting any worse and the plane landed safely.

I will also add that I had a stick shaker activation momentarily after take off one day on 34L out of SYD. We had plenty of airspeed (remember stalling isn't necessarily a loss in airspeed but when the AoA exceeds the critical angle). The reason for the activation was windshear, where a sudden change in the wind direction and speed caused the aircraft to pitch up. Because of the sudden pitch change, the stick shaker activated. It was only for a brief second or two and I was manually flying at the time so only a small nose down correction was needed to counteract. Once we were out of the shear it was a regular climb.

 

[AviatorInsight]

And how much attitude would they have lost to injure 15 when the pilot pushed the stick forward to prevent a stall?

This would depend really, it wouldn't have been a violent manoeuvre, but definitely no more than a couple of thousand feet. It sounds like a lot but it really isn't. Down lower where the air is more dense you will recover quicker. In the simulator, one of our focus as SOs at the moment (seeing as we can be on our own for a couple of minutes in the cruise) is stalling. We practice stall recovery both at altitude in coffin corner and down low. The higher altitude can take up to 5000ft (and depending on weight sometimes longer) to recover from a stall.

 

[Major]

This would depend really, it wouldn't have been a violent manoeuvre, but definitely no more than a couple of thousand feet. It sounds like a lot but it really isn't. Down lower where the air is more dense you will recover quicker. In the simulator, one of our focus as SOs at the moment (seeing as we can be on our own for a couple of minutes in the cruise) is stalling. We practice stall recovery both at altitude in coffin corner and down low. The higher altitude can take up to 5000ft (and depending on weight sometimes longer) to recover from a stall.

As a SO are you required to carry out any take offs or landings, or is this reserved until you qualify as FO ?

I gather you would also practice these in SIMs

 

[AviatorInsight]

As a SO are you required to carry out any take offs or landings, or is this reserved until you qualify as FO ?

I gather you would also practice these in SIMs

When conducting a check, take offs and landings aren't assessed. On non check sims though, we regularly do circuits just to keep our scan rate up and to keep our skills from diminishing when we get the upgrade to FO.

 

[jb747]

And how much attitude would they have lost to injure 15 when the pilot pushed the stick forward to prevent a stall?

From the FR24 data, I can't see that much of anything would have been required. It shows a minimum IAS of 226 knots, which seems about right for the slow end of the holding speeds. Stall would be well below that, something in the order of 170 KIAS. In any event recovery from the actual buffet at that level would require an attitude of about -5º and a (gentle) handful of power.

The data resolution might be hiding something, but overall the numbers don't seem bad. I can't see the 'why' in the data anyway.

 

[jb747]

New rosters out a bit earlier than usual because of Easter.

I still have one and a half London trips to do on the current roster.

Anyway, the new one:
8/5 QF 9 MEL-DXB
11/5 QF 1 DXB-LHR
13/5 QF10 LHR-DXB
16/5 QF10 DXB-MEL

27/5 QF93 MEL-LAX
28/5 QF94 LAX-MEL

4/6 QF 9 MEL-DXB
8/6 QF 1 DXB-LHR
10/6 QF10 LHR-DXB
12/6 QF10 DXB-MEL

24/6 QF93 MEL-LAX
25/6 QF94 LAX-MEL

 

[mjt57]

27/5 QF93 MEL-LAX
28/5 QF94 LAX-MEL

Miss you by a day...
But we are on that other airline that we won't mention here...

One day we will get to fly to and from the US with QF business. That is, if we are still allowed to fly to the US...

 

[clazman]

"Pacific Organised Track System (PACOTS) tracks are daily high altitude pacific routes between eastern Asia and the western coast of North-America. Eastward tracks are named numerically (1,2,3...). Similarly, westward tracks are named incrementally from the beginning of the alphabet (A,B,C...). Daily updates for each direction allow for routing around weather systems and tracking of favourable tailwinds to improve efficiency".

Who controls / organises this?

 

[clazman]

What sort of flight characteristics would the aircraft see that was dropping the MOAB on approaching and exiting the target

 

[jb747]

Who controls / organises this?

ATC, in conjunction with the airline operations centres. The pilots have nothing to do with it.

 

[jb747]

What sort of flight characteristics would the aircraft see that was dropping the MOAB on approaching and exiting the target

They used a Hercules, so I expect that a payload of 11 tonnes or so isn't that large in the scheme of things. I expect it would have been positioned to sit on the aircraft CofG. The actual parachute drawn release happened very quickly, probably without enough time to make any CofG change. But, in slow motion, as it moved aft, so would the CofG, that would cause the aircraft to pitch up. Once out of the door, the aircraft would be instantly 11 tonnes lighter, and so would be making that much too much lift. So, if you wanted to remain more or less level, you'd need a forward push on the control, nose down trim, and a reduction of power. I expect that it wouldn't be much different to an airborne cargo drop.

As I write this, I'm sitting in London, and there are articles in the paper here about the MOAB. It strikes me as a curious choice of weapon, as, being an air burst, it's not designed to operate against tunnels. I guess it would have an effect on shallow ones, but it isn't a penetrator. Also the papers are going on about it being the largest, etc. But, they need to look at a bit of history, as the RAF had two very large penetration bombs in WWII. Tall boy at 12,000lbs, and Grand Slam at 22,000. Release weight of GS and MOAB are almost identical.

 

[RooFlyer]

<snip>

As I write this, I'm sitting in London, and there are articles in the paper here about the MOAB. It strikes me as a curious choice of weapon, as, being an air burst, it's not designed to operate against tunnels. I guess it would have an effect on shallow ones, but it isn't a penetrator. Also the papers are going on about it being the largest, etc. But, they need to look at a bit of history, as the RAF had two very large penetration bombs in WWII. Tall boy at 12,000lbs, and Grand Slam at 22,000. Release weight of GS and MOAB are almost identical.

I thought 'biggest' etc referred to the (non nuclear) explosive power? The article in the Oz also noted this:

A separate non-nuclear weapon known as the Massive Ordnance Penetrator, or MOP, which is larger in its physical dimensions but carries a smaller load of conventional explosives, is designed to take out deeply buried targets like reinforced bunkers.

 

[Boca68]

They used a Hercules, so I expect that a payload of 11 tonnes or so isn't that large in the scheme of things. I expect it would have been positioned to sit on the aircraft CofG. The actual parachute drawn release happened very quickly, probably without enough time to make any CofG change. But, in slow motion, as it moved aft, so would the CofG, that would cause the aircraft to pitch up. Once out of the door, the aircraft would be instantly 11 tonnes lighter, and so would be making that much too much lift. So, if you wanted to remain more or less level, you'd need a forward push on the control, nose down trim, and a reduction of power. I expect that it wouldn't be much different to an airborne cargo drop.

As I write this, I'm sitting in London, and there are articles in the paper here about the MOAB. It strikes me as a curious choice of weapon, as, being an air burst, it's not designed to operate against tunnels. I guess it would have an effect on shallow ones, but it isn't a penetrator. Also the papers are going on about it being the largest, etc. But, they need to look at a bit of history, as the RAF had two very large penetration bombs in WWII. Tall boy at 12,000lbs, and Grand Slam at 22,000. Release weight of GS and MOAB are almost identical.

As a minor correction, the GBU-43 (aka MOAB) is designed to be airburst, but can contain delayed metrics. Using its GPS targeting, it can be altered live via operator. Meaning, especially on soft targets, it is able to detonate slightly after impact. Even without the delay mechanism its airburst point is less than 30 metres. So, with the delay is able to penetrate soft targets at up to 5 metres below ground before detonation.

I believe but don't quote me, the target in Afghanistan was in a quite soft sandy area. Hence the frequency of tunnels and below ground infrastructure. Also had an effect on the decision to employ this ordinance .

Now, its effectiveness, is most likely severally retarded in these situations. Even though, I don't think I would enjoy being in close vicinity.


edit: now, the reasons given for this "historic military action"...... draw your own conclusions? How many 'daisy cutters' were dropped over the last 15 years? Sure its a big bomb, but in the scheme of things, means diddly squat



1

 

[jb747]

Harking back to an earlier time...the A4G weapons panel allowed us to use multiple fuses on a bomb, so we could select which fuse to use, and the type of burst. The settings were E, F, H, G, S....which we remembered as "early, fast, hard, granite, special", and that's probably why I still remember them.

Early was a proximity burst. Fast was instantaneous. Hard was a short delay, and G a long delay. S meant 'special'.

The normal setup was to use a mechanical nose fuse (which we could not alter the settings of in flight), and to interconnect that with a 'snake-eye' retarder tail. If the weapon was released using the nose fuse, the tail would also open. If we used the tail electronic fuse (that gave us the settings), the fins would remain closed, and the bomb would go in the low drag, 'slick' configuration.

The term 'daisy cutter' was actually applied to bombs with an extended nose fuse. Basically the fuse was mounted on a pipe about two feet ahead of the normal position. Coupled with an instantaneous burst, that would cause it to go off just a few inches above the ground...at the height of the daisies. Images of them are common from the Vietnam war.

In this image, the bombs on the wing stations have daisy cutter fuses, which the weapons on the centreline don't.

 

[Boris spatsky]

They used a Hercules, so I expect that a payload of 11 tonnes or so isn't that large in the scheme of things. I expect it would have been positioned to sit on the aircraft CofG. The actual parachute drawn release happened very quickly, probably without enough time to make any CofG change. But, in slow motion, as it moved aft, so would the CofG, that would cause the aircraft to pitch up. Once out of the door, the aircraft would be instantly 11 tonnes lighter, and so would be making that much too much lift. So, if you wanted to remain more or less level, you'd need a forward push on the control, nose down trim, and a reduction of power. I expect that it wouldn't be much different to an airborne cargo drop.

We used to drop 35000 pound bulldozers in the Herc - attached to a pallet. Loaded around the C of G near the main wheels. Pretty hairy to drop as if the load gets stuck on exit you can exceed the ability to fly away due to an extreme C of G and massive drag of the multiple parachutes (3 or more).

Once the load exits you get a distinct nose up pitching tendency. We used to train for platform 'hang ups' in the aircraft and sim and it was pretty full on.

 

[Quickstatus]

Have there been actual cases of hangups?

Whats the usual time to eject a load?
Usual Aircraft speed at the time?
Does the aircraft position according to prevailing winds at altitude?