Air brakes: are they supposed to be "On/OFF" only?

[Nealius]

That makes a whole lot more sense now that I think about my landing experiences with the M2000 so far.

[IvanK]

+1 Nerd1000

[Sarge55]

Explains why I dropped like a rock the last couple of meters to the runway when I first started landing. Really need to keep the power on right to touch down.

[Robin_Hood]

Deltas don't stall like aircraft with straight wings- on a straight wing, exceeding critical AoA tends to result in a rapid decrease in lift and a equally rapid increase in drag. Deltas don't lose lift as quickly, but the drag increases dramatically like on other wings.

 

This means that it is possible to get into what I call 'the hole' where the aircraft is still under control and producing lift but the wing is making vast amounts of drag, so much that you might find yourself needing to use full dry thrust (or maybe even more!) just to maintain your current speed. The only way to escape is to lower the nose and accelerate or use full afterburner to power out of it.

 

This is true of other aircraft as well, not only Deltas. A famous example is the Sabre Dance video, where an F-100 is trapped in this situation, too low to get our of the trap ; it does not end well.

 

Concerning the saying, I think the confusion may be that the very phrasing can be somewhat imprecise. It is not that "Throttle is what controls altitude and Stick is what controls airspeed", but more that "You should control altitude (better, sink rate / glide path) with the throttle and airspeed (better, AoA) with the stick". This way it does not imply that throttle has no effect on airspeed, it simply tells that the primary means of controling AoA is the stick and the primary means of controlling glide path is the throttle.

 

I am not sure how it is on the Mirage, but some FBW aircraft do in fact maintain (at low airspeeds) AoA for stick position (instead of, usually, Gs at higher airspeeds). In this case, you are very much setting your AoA with the stick and then adjust the throttle so that your glide path is right.

[jojo]

This is the case for real Mirage.

Below 300kt you control mostly AoA.

Above 300kt you control mostly G.

[Nealius]

On a related note, what's the maximum speed you can have the LG down? I read that the gear should come down at 230kts, but on takeoffs with two wing tanks and two Magics the jet frequently exceeds 200kts before even getting airborne, so I'm wondering where the 230kt figure came from.

[Nerd1000]

This is true of other aircraft as well, not only Deltas. A famous example is the Sabre Dance video, where an F-100 is trapped in this situation, too low to get our of the trap ; it does not end well.

 

Concerning the saying, I think the confusion may be that the very phrasing can be somewhat imprecise. It is not that "Throttle is what controls altitude and Stick is what controls airspeed", but more that "You should control altitude (better, sink rate / glide path) with the throttle and airspeed (better, AoA) with the stick". This way it does not imply that throttle has no effect on airspeed, it simply tells that the primary means of controling AoA is the stick and the primary means of controlling glide path is the throttle.

 

I am not sure how it is on the Mirage, but some FBW aircraft do in fact maintain (at low airspeeds) AoA for stick position (instead of, usually, Gs at higher airspeeds). In this case, you are very much setting your AoA with the stick and then adjust the throttle so that your glide path is right.

 

The 'Sabre dance' is a different phenomenon, namely the outer part of a highly swept wing stalling before the inner part, causing the Aerodynamic centre of pressure to move forward. This results in an uncontrollable pitch up.

 

In the situation I'm describing the pilot still has control of the plane but the outcome of control inputs may be counter intuitive (for example: pitching up increases rate of descent).

 

You can see what happens when things go wrong under those flight conditions in this video:

The F/A-18 shares some of the high AoA characteristics of a delta thanks to its LERX surfaces, which is why it is able to perform the high AoA low speed pass in the video. In this case, however, the pilot was too low to recover by lowering the nose and his attempt to power out of the 'hole' using afterburner was foiled by an engine failure. The asymmetric thrust then sent the plane into an unrecoverable spin.

[NeilWillis]

On a related note, what's the maximum speed you can have the LG down? I read that the gear should come down at 230kts, but on takeoffs with two wing tanks and two Magics the jet frequently exceeds 200kts before even getting airborne, so I'm wondering where the 230kt figure came from.

 

It might be simple to answer this, but as you want to include every factor in your answers, I shall just say it depends on air temperature, altitude, and the metorological air pressure that prevails at the time you ask the question.

 

It might be simpler to just give a ballpark answer, but it seems it isn't good enough here, so the correct answer is..

 

I depends on too many variable factors to give you a correct answer without over-simplifying it!

[Nealius]

No reason to be a smartass. I asked a simple question.

Edited January 29, 2016 by Nealius

[NeilWillis]

under 260 knots is the figure stated in the manual.

 

Being a smartass wasn't my position originally, I was simply going along with how you like questions answered. I'd hate to over simplify things just because they happen to be correct.

 

So, whichever position suits you, I'm happy with it. As long as it is made clear when you ask the question whether you want the answer, or all the science that goes along with it. Simply put, you don't need a degree in physics to know that something happens, only to know how and why it happens.

 

Point made now?

[Nealius]

Typically it's clearly stated in the flight manual so there really wasn't much need for that...

 

I saw where the RAZBAM manual says 260kts but then it contradicts itself with 230kts, and I can't read French so the real manual wasn't helping either.

[NeilWillis]

It doesn't say 260 knots it says UNDER 260 knots to raise the gear, and lower below 230 knots.

 

I see nothing contradictory about raising the undercarriage at an airspeed below 260 knots, and lowering the undercarriage at an airspeed below 230 knots.

 

It is as clear as day in the manual. This is your question:

 

On a related note, what's the maximum speed you can have the LG down? I read that the gear should come down at 230kts, but on takeoffs with two wing tanks and two Magics the jet frequently exceeds 200kts before even getting airborne, so I'm wondering where the 230kt figure came from.

 

The answer was below 260 knots, which as you asked the maximum speed with lowered gear, was in fact exactly what you asked for was it not?

 

However, you would wait until your airspeed was below 230 knots when you deploy it.

 

Nothing contradictory there at all.

[Fab]

Hmmmm, I wonder at what speed, the undercarrige will be damaged ? ( I know air tempeture and ASL is a factor, but there must be a Kt vs QNH doctrin for safe operating of the plane ?

I wond if the below 230kt lowering your undercarrriage, is because its deployed by the help of its own weight, and cant lock, if speed is higher?

[jojo]

Guys, do you really think that there is a table of pressure altitude Vs speed to lower/ retract landing gear ?

 

Pilots need some simple rules. This is single seat fighter.

[Fab]

Guys, do you really think that there is a table of pressure altitude Vs speed to lower/ retract landing gear ?

 

Pilots need some simple rules. This is single seat fighter.

 

Might not be for the pilots, but I bet the factorey got one :smilewink:

[jojo]

Since HUD speed is CAS, pretty sure it works well.

 

You really like to look for complications...:(

[Sarge55]

I hope this isn't going to turn into another "Chat Fight". It's getting a bit tiresome.

[Nealius]

The only reason I said the 230/260 was contradictory is because I'm used to flight manuals that give a straight and hard single figure like "do not lower gear above 300kts" and that's it.

 

I'm done with this. Your attitude is getting on my nerves.

Edited January 30, 2016 by Nealius

[NeilWillis]

 

I'm done with this. Your attitude is getting on my nerves.

 

That's rich coming from you! We tried hard to help you in the first place, and what did we get? If you want answers, then kindly don't try telling the ones who are trying to help that they're wrong - especially when they are right, even if it is a simplification, it is still just as valid, and just as effective. Evidence would suggest the simple answer was what you really needed anyway!

 

My first answer regarding landing gear V-max was entirely in line with what you pointed out in your criticism of earlier answers.

 

Why is a different speed for retraction and deployment in the slightest bit contradictory? The higher speed at take-off actually helps with your high rotation speed issue with a lot of stores aboard, and the difference is just the difference. What doesn't make sense about any of it?

[=DECOY=]

Seriously all I see nowadays on this forum is bickering and arguing.

 

Has this site turned into a jerry springer forum!!!

 

can't we just get along :(

[cauldron]

power for altitude and pitch for speed

 

Couldn't agree more; it's a foolish statement and an oversimplification.

 

 

A stable approach requires good energy management and you can't state one control affects one aspect and one control affects another when they're all interconnected.

 

You guys are taking the phrase out of context, its absolutely true when you in context. The context being that you are on, or near, a stable approach to landing and need to make an "adjustment" to your approach... low speed --> reduce your drag a bit (pitch), descending too fast --> increase excess thrust i.e. add power. These are for making fine adjustments to a landing approach, and are tried and true methods of instruction because if your within the context of the instruction ;) they help teach how to make changes that help, and not changes that will de-stabilize your approach.

 

So, you are right, if you take it out of context, and you are wrong if you are in the context of that instruction. If you don't believe me go out and try next time you are on a final approach: for ONE example: you'll find that if you initially set for proper pitch & power get on the appch path, that deviations in speed are usually pilot induced by pitch and that "getting slightly slow" has come with a tad of "too high" and thus the best response is pitch, not power, because your power is mostly set anyways, this is also assuming no wind sheers which have their own set of complications to deal with.

 

All i can say is there is a very real reason for this universal teaching mechanic, and i suggest trying to find out why it works and when and why and when it doesn't - as it would only make for better pilots. But please, its not just a statement, and far from 'foolish', its been paid for in real blood and hard learned. It's not meant to be taken literally, as it has many variations, its a teaching tool which as all tools go can be misused - but if its used as the right way its a great and effective teaching tool for a pilot dealing with all the sensory input which happens in flight.

 

Edit: I am assuming the thread can get back to a friendly debate, otherwise i'm sorry for "bumping" a thread that's gone sour.

Edited February 1, 2016 by cauldron
i read the later posts, jeez....

[JulietAlfaMike]

power for altitude and pitch for speed

 

All i can say is there is a very real reason for this universal teaching mechanic, and i suggest trying to find out why it works and when and why and when it doesn't ...

 

Edit: I am assuming the thread can get back to a friendly debate, otherwise i'm sorry for "bumping" a thread that's gone sour.

 

As the original topic was around approach/airbrake -problematics, I would like to contribute in the friendly debate mood...

 

If delta wing aerodynamics is unfamiliar there is some theory that is worth considering. Even though it is a bit boring...well, I try to express myself in a practical way. I think the complex relation between AoA - Pitch - thrust is already pointed out but the induced drag - aerodynamic lift - high AoA problematics is something that might not be too clear to everyone.

 

Compared to for example A-10 the Mirage 2000 approach can be called a high AoA situation. Thus the change in pitch/AoA and thrust with M2000 are proportionally different from A-10. Increase AoA and you add more induced drag but also your thrust vector in relation to your flight path decreases and the increase in lift is less because the lift vector points more backwards than before.

 

So to avoid simultaneous increase in pitch/AoA and decrease in thrust I think the advice to use thumb rules in approach is very advisable. I prefer to use the airbrake the way it's done in real life if I just know it. In any case I wouldn't "use" airbrake during final approach for the sake of safety. Truly superior pilots know how to avoid situations which superior pilots can handle... Long steady final if you are not running on fumes ;)

[Corsair]

Hmmmm, I wonder at what speed, the undercarrige will be damaged ? ( I know air tempeture and ASL is a factor, but there must be a Kt vs QNH doctrin for safe operating of the plane ?

I wond if the below 230kt lowering your undercarrriage, is because its deployed by the help of its own weight, and cant lock, if speed is higher?

 

What ??

Just read your CAS.. below limit, it's safe, above, it's not, whether you're at 500 or 45 000 ft...