DCS A-10C QUESTIONS

[Laud]

So is it a remain from an older version, as the flaps retract automatically?

 

That's all it is.

[GGTharos]

I believe so. I'm not aware of any aircraft having 'maneuver' markings on their IAS instrument, since the IAS changes with altitude. At 30000' you might find yourself flying at 180kt or less, and you won't be sustaining squat at that altitude anyway ;)

[EtherealN]

I believe so. I'm not aware of any aircraft having 'maneuver' markings on their IAS instrument

 

Gliders is all I can think of. Though in that case it's "best glide ratio" and not related to G loading and so on.

[Laud]

However, the article is a good find anyway.

[JS]

I just found this on the DCS Wiki: http://www.dcswiki.com/index.php?title=Airspeed_indicator_%28A-10%29

"A yellow tick mark outside the scale at 200 knots indicates the maximum speed at which landing gear and flaps may be extended."

 

Even though the mark is clearly above 200 knots, it seems to confirm that it is indeed related to the flaps (and landing gear). However, the information about the sustained turn performance in the blog post is still very relevant, and after reading it again I see it is not explicitly stated in that post that the mark is related to this, just that it happens to be the same as the breaking point speed for sustained turn performance.

Edited April 20, 2011 by JS

[genbrien]

IIRC the flaps wont go down above 180kt.

And I extended the gears wayyyy above 200kt and nothing hapened.....

[Scratchy]

I just found this on the DCS Wiki: http://www.dcswiki.com/index.php?title=Airspeed_indicator_%28A-10%29

"A yellow tick mark outside the scale at 200 knots indicates the maximum speed at which landing gear and flaps may be extended."

 

Even though the mark is clearly above 200 knots, it seems to comfirm that is indeed related to the flaps (and landing gear). However, the information about the sustained turn performance in the blog post is still very relevant, and after reading it again I see it is not explicitly stated in that post that the mark is related to this, just that it happens to be the same as the breaking point speed for sustained turn performance.

 

I have my doubts about the Wiki entry.

 

landing gear...but they should only be lowered when below 250 knots.

 

If airspeed exceeds 185 KIAS, the flaps cannot be extended. If the flaps are extended and the aircraft reaches 185 KIAS or greater, the flaps will automatically retract to the UP position.

 

These are the only 2 hard airspeed restrictions that I've seen in the manual. Maybe that's the only ones. The barber pole is the Vne and the stall warning is the other end of things.

 

I tend to agree with the above linked article as he did quote a USAF publication.

[BlueRidgeDx]

The yellow line is the limit speed for gear and/or flaps down.

 

Early A-model airplanes had the flap auto retract function, but the auto-deploy function (when decelerating through the limit speed with the flap handle in MVR or DN), was retrofitted later.

 

Nonetheless, 200 knots is still the limit speed for gear extension, and it provides a cue for flap auto extension/retraction, thus it is retained.

[Frederf]

I believe so. I'm not aware of any aircraft having 'maneuver' markings on their IAS instrument, since the IAS changes with altitude. At 30000' you might find yourself flying at 180kt or less, and you won't be sustaining squat at that altitude anyway ;)

 

IAS, or rather CAS, is the best airspeed to correlate to maneuver potential. 200 KCAS at sea level and at at 30,000' give similar aerodynamic performance. Thus a typical airspeed indicator is the best candidate for having fixed markings relating to maneuvers and airframe limits.

 

Physics first, smirky emote faces later.

[GGTharos]

Hold the same G at the same IAS at those two different altitudes, then come back and see if you want to say this again. ;)

 

Physics first, smirky emote faces later.

[EtherealN]

IAS, or rather CAS, is the best airspeed to correlate to maneuver potential. 200 KCAS at sea level and at at 30,000' give similar aerodynamic performance. Thus a typical airspeed indicator is the best candidate for having fixed markings relating to maneuvers and airframe limits.

 

"Best" possibly, but I'm not convinced about it being particularly useful anyhow. The fact that inertia doesn't change, for one thing, causes issues with the utility of this. Even more important would be the particulars of how engine thrust changes with altitude and your marking will quickly become a detriment rather than an aid.

Edited April 20, 2011 by EtherealN

[JS]

I have now had it confirmed from the author of the blog post I linked to that he indeed did not intend to imply that the yellow mark on the airspeed indicator is related to this. He was just explaining the importance of 210 knots IAS when making sustained turns, and noted the mark that is located at around that number on the airspeed indicator.

 

He uses that mark as a reference when doing combat maneuvers, but says he made no claim about the reason why it is there.

[aaron886]

"Best" possibly, but I'm not convinced about it being particularly useful anyhow. The fact that inertia doesn't change, for one thing, causes issues with the utility of this. Even more important would be the particulars of how engine thrust changes with altitude and your marking will quickly become a detriment rather than an aid.

 

That doesn't really make sense... of course inertia is identical at altitude, but this is aerodynamics. The gear extension speed is the airspeed at which air resistance can damage the gear... it's not really designed to encompass centripetal forces, AFAIK.

 

Indicated/Calibrated is the "only" airspeed to refer to in this case.

[EtherealN]

aaron886, we were talking about using such permanent marks for maneuver guidelines (like a "max sustain" etc) - not the actual use as FLAPS/gear.

[Bimbac]

I believe so. I'm not aware of any aircraft having 'maneuver' markings on their IAS instrument, since the IAS changes with altitude. At 30000' you might find yourself flying at 180kt or less, and you won't be sustaining squat at that altitude anyway ;)

 

Hold the same G at the same IAS at those two different altitudes, then come back and see if you want to say this again. ;)

 

Hello again :)

 

IAS (indicated airspeed), also referred to as Instrument Airspeed, is the primary means of reading the airspeed. However, it doesn't change with altitude (true airspeed TAS does). So the stall speed indicated on the flight instrument will be same when flying at sea level or at 30000 feet - so it makes a perfect sense of marking the IAS instrument with certain speeds, because it will work all the time (notice the Airspeed Indicator in Su-25, for example).

 

A Pitot tube senses both dynamic and static air pressure. Dynamic air pressure is used for measuring the airspeed, static pressure for altitude. Since the air density decreases while the altitude increases, you must fly at higher airspeed in order to stay airborne. So the IAS will be the same, but TAS will be higher than at sea level.

 

I hope you don't mind my choppy explanation.

 

Regards!

[GGTharos]

Nope, it's a fine explanation - your first sentence had me thinking you confused something at first, but the rest of it clarified :D

[Bucic]

Since the air density decreases while the altitude increases, you must fly at higher airspeed in order to stay airborne. So the IAS will be the same, but TAS will be higher than at sea level.

I remember the time when I tried to figure out what is the pilot's airspeed indication i.e. which is the most important to the pilot / which will allow a reliable and rather precise stall speed indication and "riding on the edge of flight envelope".

 

When in doubt always refer to the freely available

[Frederf]

Hold the same G at the same IAS at those two different altitudes, then come back and see if you want to say this again. ;)

 

I will say it again. At 210 KIAS/KCAS you will get the same performance at 1,000' as 25,000'. Now you're saying "Oh well if you have a weak engine at altitude you can't keep up this speed for long." But this is completely beside the point since I said that at the same IAS/CAS aerodynamic performance is the same. You come back with "well what if you slow down?" Well then it's not going to be the same speed is it?

 

"Best" possibly, but I'm not convinced about it being particularly useful anyhow. The fact that inertia doesn't change, for one thing, causes issues with the utility of this. Even more important would be the particulars of how engine thrust changes with altitude and your marking will quickly become a detriment rather than an aid.

 

Stall speed, corner speed, instantaneous turn speeds? Those are all maneuver speeds very much tied to IAS. I'm saying as far the aircraft's agility and health is concerned, IAS is king. TAS is meaningful only in navigation.

[EtherealN]

I will say it again. At 210 KIAS/KCAS you will get the same performance at 1,000' as 25,000'. Now you're saying "Oh well if you have a weak engine at altitude you can't keep up this speed for long." But this is completely beside the point since I said that at the same IAS/CAS aerodynamic performance is the same. You come back with "well what if you slow down?" Well then it's not going to be the same speed is it?

 

But if the plane will slow down up there, as it will do, marking for it is pointless. That's the point. You don't mark instruments based on a theoretical perfect-world condition - especially not an A-10C that lumbers to even stay airborne at high altitudes if you've loaded it down with weapons.

 

Stall speed, corner speed, instantaneous turn speeds? Those are all maneuver speeds very much tied to IAS. I'm saying as far the aircraft's agility and health is concerned, IAS is king. TAS is meaningful only in navigation.

 

Stall speed at which weight, configuration and attitude? 45k LB clean configuration gives me 135 KCAS. 30k LB clean gives me 110 KCAS. Or should we go for 25k LB landing configuration? That's 108 KCAS. Pick which one you want marked.

 

And on Instantaneous turn, where will you mark that? 20K feet gives me 300 KIAS and 5.6G at 30k LB. 30k feet gives me 240 KIAS and 3.7G. 15k feet gives 360KIAS for 6.6G at 30k LB.

 

THAT is the point. Permanent markings like that are not useful. :)

[Frederf]

We agree that flight performance marks on the IAS are only useful in such specific instances as not to be worth marking for general flight. Hopefully we also agree that CAS is also a good indicator of how many and how strong the air molecules are flowing around the airplane surfaces.

 

What confused the bejebus out of me was Tharos's

not aware of any aircraft having 'maneuver' markings on their IAS instrument, since the IAS changes with altitude.

It seemed to suggest that the reason that one does not mark their ASI is because "IAS changes with altitude." I couldn't follow that logic. If IAS didn't change with altitude would it make sense to mark the ASI? If you had a TAS gauge would it make sense to mark it then? What does that "A since B" mean?

 

I though, that makes no sense. If you were going to mark any type of gauge for maneuvers it would be the ASI! Because the ASI does what it does it does the way that it does it makes the best candidate for marking.

[EtherealN]

I think what he means is that the desirable IAS for a given maneuver changes with altitude. (And, for that matter, atmospheric conditions, drag index, weight and such can play a role as well.)

 

Though, to be nitpicky, I don't quite agree about the "how strong" air molecules and CAS. The relative energy of an individual molecule goes up as square of velocity, but since we're not talking about abrasion of the paint on the plane or something like armoring spacecraft... Not exactly relevant. So yeah, agreed. :)

[Frederf]

I took it to mean that IAS for a given TAS changes with altitude, which while true, was confusing how it related.

 

Think momentum, not energy. Perhaps I should say air pressure instead of "strength." Air pressure around a lift or control surface at a certain CAS tends to be pretty constant with change in any other variable (temperature, altitude, humidity). If you have a service door flapping in the breeze it will tend to rip off at X KCAS no matter what condition that CAS was achieved.

[EtherealN]

Aye, pressure instead of strength and we'll be 100% on the same page.

[Frederf]

While I'm here I know I have many questions about things A-10 related but I won't be able to think of them all at once. I'll start with a few off my head:

 

What are the min/max settings the (looks up what the model of the altimeter is)... oh nevermind. It's the AAU-34/A altimeter and it has an adjustment range from 28.1" to 31.0" http://www.kollsman.com/downloads/Altimeter%20AAU%2034A.pdf

 

Ok for real now. Is the Anti-Skid switch solenoid-held, spring-loaded?

[Olgerd]

Ok for real now. Is the Anti-Skid switch solenoid-held, spring-loaded?

 

Yes it is.