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RCS?

The tail isn't used to generate rolling motion, so it really doesn't matter all that much how far it is from the roll axis.

Equivalent surface area? To what? A bigger single tail? True to a degree, but why would you need a bigger tail, or more area. Why did the SR71 have three vertical surfaces? The Tornado has a single fin, but quite massive.

These aircraft are all very fast...the reason is to be found there.
RCS is radar cross section, I'm guessing.

The later Spitfire marks had clipped wings - squared off, rather than that elegant curve - to improve roll rate. Sacrifice a little lift to avoid paddling those extremities sideways through the air.

So I'm guessing that shorter tails would have some effect, but probably not a lot.

Would it be something to do with the supersonic shock region? A single tail would be fair in the middle, but twin tails might bite into the clear air outside the cone.
 
RCS?

The tail isn't used to generate rolling motion, so it really doesn't matter all that much how far it is from the roll axis.

Equivalent surface area? To what? A bigger single tail? True to a degree, but why would you need a bigger tail, or more area. Why did the SR71 have three vertical surfaces? The Tornado has a single fin, but quite massive.

JB, yes Radar Cross Section - sorry, I would have thought that two small tail surfaces would be a lot better than one big slab o' tailfin especially if there's somebody trying to shoot bullets or get a missile lock on you. I didn't think the SR71 had three vertical surfaces - only the two inwardly canted fins above the engine nacelles?

Reading up a bit more on the SR71, I'm thinking it would be something along the lines of what Skyring was saying about supersonic shock but also possibly due to shock waves / air flow patterns off the leading edge extensions that appear to common on most fast jets. The other thing that may add credence to this is that most modern twin tails are canted to some degree?
 
I didn't think the SR71 had three vertical surfaces - only the two inwardly canted fins above the engine nacelles?

It folded down from the bottom. It wasn't on all of the variants.

Normally as you fly faster, you have increased lift (on all surfaces). The coefficient of lift is relatively constant. But as you approach the speed of sound (from about .9 mach), the C/L starts to decrease. It will probably go to a value around half of normal as you approach mach 1. On the far side, it recovers, but to a level appreciably less than it was originally. Upshot is that directional stability can become an issue, so you need a very tall tail, a couple of them, or an unusually long moment arm.

And of course a whole bunch of other factors come into play too, to make a design attractive or not.

The same effect was the cause of an effect known well to Mirage pilots, called transonic tuck.
 
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Often the 2 vertical stabilisers are canted thus giving pitch and yaw input. Have you ever piloted these aircraft?

No. When the navy lost the A4Gs, that was the point at which I bailed out and joined the airlines. Some of my friends did move to the RAAF, and flew Mirage and F18. Amazingly, six of the surviving A4Gs are still flying with a contract aggressor mob in the USA (Draken).
 
Not a pilot , nor an expert, but are not dual stabilisers apart from nominal stability as jb747 states, also improve performance when carrying external weapons/drop tanks on the wings and underside?

As the aircrafts' drag is affected by the external pods, having dual stabilisers improves performance over a single larger stabiliser?
 
Was this related to the decommisioning of the HMAS MEL?

Sure was, and as I recall from my Navy days, we passed them on to the RNZAF for free or 'el cheapo', and then had to pay the Kiwis to fly them back to be used against us in anti aircraft training exercises. Good move on our part.
 
Can you please confirm on board wifi availability when on the ground? I understand most services only allow you to connect when up in the air but I heard there is wifi that the pilots have access to when on the ground.
 
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Can you please confirm on board wifi availability when on the ground? I understand most services only allow you to connect when up in the air but I heard there is wifi that the pilots have access to when on the ground.

Overseas we just use 4G dongles, which are collected by the ground staff before the doors close. Within Oz, the iPads are all 4G connected.

And we also select flight mode when the doors are closed too.
 
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Boris - this might sound like a dumb question (sorry), but do all pilots have equal levels of confidence when it comes to the sort of weather we saw on the weekend? For example, would you ever find a pilot who was brave enough to admit she/he didn't have the experience required to feel confident taking on those winds (and rain and reduced visibility etc.)?
 
Yes, from my experience they do. The flightdeck is not a place to be if you have a lack of confidence.
Beg pardon, but that's not quite answering the question. Having or not having confidence in flying abilities is one thing. Being brave enough to admit it, another.

I know an ex-RAAF pilot who is obsessive about safety. The sort of guy who checks everything three times. Decades of experience. I think if he was uncomfortable about flying in certain weather conditions, he would admit it, whereas a younger guy might not.

While I would prefer my pilots to be experienced and confident, I also want them to be honest rather than foolhardy. I notice some planes diverted last weekend, and I'm guessing that was weather-related, and the pilots accepted that in a highly visible way.

I guess the question might be rephrased as "when does an airline pilot admit that the weather is beyond the abilities of himself or his aircraft?"
 
Beg pardon, but that's not quite answering the question. Having or not having confidence in flying abilities is one thing. Being brave enough to admit it, another.

I know an ex-RAAF pilot who is obsessive about safety. The sort of guy who checks everything three times. Decades of experience. I think if he was uncomfortable about flying in certain weather conditions, he would admit it, whereas a younger guy might not.

While I would prefer my pilots to be experienced and confident, I also want them to be honest rather than foolhardy. I notice some planes diverted last weekend, and I'm guessing that was weather-related, and the pilots accepted that in a highly visible way.

I guess the question might be rephrased as "when does an airline pilot admit that the weather is beyond the abilities of himself or his aircraft?"

I am sorry you thought I was not answering the question - now that I am back home on a desktop computer I can give a more thorough answer.

There are strict limits for aircraft with respect to items like crosswind and visibility for takeoff and landing. The aircraft is certified to a set limit, so you don't go over it unless in an emergency situation. Simple as that. The limit is also a certification demonstrated limit - that doesn't mean that every pilot is capable of operating right up to that limit. In that case, the operator may impose more stringent limits - for example, the demonstrated crosswind limit might be 35 knots, but that may be reduced in wet weather, on narrow runways, when some items like thrust reversers or spoilers are unserviceable, or when the First Officer or new captain is flying. Those limits would be found in the operations manual for the operator.

Visibility for takeoff and landing is a set figure - you either have it, or you don't. You also have contingencies in case the visibility reduces after you have commenced the procedure - for example, we have an additional low visibility briefing in the flightdeck in low vis takeoffs that includes actions to take if the visibility reduces at high speed before rotation.

So as you can see, there are stringent requirements that must be met - and the training trains to those limits. You don't just get thrown in an aircraft and try your first maximum crosswind landing unsupervised - it just doesn't happen (at least in Australia).

There are of course times when the limit is beyond the abilities of the crew or the aircraft - and then it comes down the crew. Decision making processes are trained for and assessed - holding airborne or delaying on the ground due to the inclement weather, picking who will fly the approach and how the crew will operate or choosing an alternative route are all options that are considered in periods of bad weather.

We are all obsessive about safety - or we wouldn't be in the airlines. I don't think many pilots in RPT operations in this country are 'fool hardy' as you put it - there is just no place for that with passengers down the back. Yes, being uncomfortable does happen (severe turbulence is never fun, nor is serious windshear on takeoff or landing) - I generally won't be acknowledging it airborne because I will be managing the situation with fairly high workload. But I am all for a debrief on the ground with the crew as a discussion point.
 
Apologies if this has been asked before :
It has always puzzled me that on US domestic flights there is no requirement to have the window shades up. In fact most flights have them all down upon boarding and they stay that way.
I assumed that this was due to it not being a requirement of US authorities and wondered if the pilots here thought it could potentially be a safety issue with passengers having no visual of the outside in the event of an emergency ?
 
Apologies if this has been asked before :
It has always puzzled me that on US domestic flights there is no requirement to have the window shades up. In fact most flights have them all down upon boarding and they stay that way.
I assumed that this was due to it not being a requirement of US authorities and wondered if the pilots here thought it could potentially be a safety issue with passengers having no visual of the outside in the event of an emergency ?

There is an argument that the shades being up allows the crew inside to assess conditions outside before firing off a slide into the middle of a fire, or conversely it allows rescue staff to look inside.
 
There is an argument that the shades being up allows the crew inside to assess conditions outside before firing off a slide into the middle of a fire, or conversely it allows rescue staff to look inside.
And to provide natural light to aid in getting out of the 'plane, too, I guess...
 
Boris - this might sound like a dumb question (sorry), but do all pilots have equal levels of confidence when it comes to the sort of weather we saw on the weekend? For example, would you ever find a pilot who was brave enough to admit she/he didn't have the experience required to feel confident taking on those winds (and rain and reduced visibility etc.)?

Another simple sounding question....

Airlines train to set limits, which aren't generally to broken, unless an overriding emergency exists. So, I guess there's a basic level of skill across the board. But, some pilots will be exposed to flying on the limits much more often than others, and so may actually be better at handling them.

Confidence is a dangerous term. Misplaced confidence is the cause of many accidents. Experience and confidence gives you the ability to say NO. I've discontinued an approach and diverted (in Europe) when some other aircraft were landing. Given that the people who were landing were what I'd call the 'usual suspects', I'm quite happy with my decision. The company didn't question it.

In the weather that existed in Sydney the other day, there are some aircraft that I'd rather be flying than others. The 767 would generally be at the top of that list.
 
Confidence is a dangerous term...
In the weather that existed in Sydney the other day, there are some aircraft that I'd rather be flying than others. The 767 would generally be at the top of that list.

Thank you, JB - appreciate the response, and certainly agree with your comments about 'confidence' often being more a case of knowing when to say 'no', rather than 'sure, I can do this'.

We were on a B717 going out of SYD. I wasn't much looking forward to the flight given I had trouble walking from the hotel to the can without being blown over, but as it turned out, ended up being a really smooth flight. Few small bumps on the way out and way in (to CBR), but full service and all normal otherwise.
 
I am sorry you thought I was not answering the question - now that I am back home on a desktop computer I can give a more thorough answer.

Thanks Boris - I wish I had something more substantial to say than, "what a great answer"!

I'm sure I speak for many others when I say how incredible it is to have someone with your knowledge and experience so readily available. Thanks again mate!
 

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