FS2004 Airfile table 1502

[WarpD]

The setting that gives me 93%n2 reverse is -41 still with the same tables.
The only thing is that it's quite slow to get there. I suppose because it starts from 56% idle and thus follows the 1505 curve back up to 93%.
vololiberista

-41 would be 4100% of throttle. That value is only valid from 0 to -1 in fractional amounts.

An entry such as this:

min_throttle_limit=-0.250000

Would result in reverse thrust that represents 25% of the physical throttle movement.

 

[vololiberista]

But -25 doesn't give me 93%n2
vololiberista

 

[WarpD]

Are you intentionally leaving out the decimal point??? There should be a decimal point.

 

[vololiberista]

No I'm quoting from the airfile which has the same number. It's a bit confusing as to which number is actually being used.
The cfg. has -0.41 and the airfile has -41
vololiberista

 

[WarpD]

I have no idea why you have an entry for this in the .air file... as it's no longer required for FS9 nor FSX.

 

[vololiberista]

All my a/c have an entry for reverse thrust in their airfiles. However!
my table 1505 is still a little sluggish from 56% to 75%. I need to try and take about a second and a half out of that to be close enough to the real engine spool up.
vololiberista

 

[vololiberista]

What I've also discovered is that adding the code below the engines will spool up in reverse from wherever they happen to be at the moment the throttle is closed and reverse set. In other words they don't run down to idle then spool up as before. For example coming in to land the throttle will be about 80+%. As I flare I close the throttle, the engines are still running down upon landing. I select reverse and up they go to 93%. I need to take about half a second off that and we're home and dry.
vololiberista

<Value>(A:Turb eng1 N2, percent) s0 (A:General eng1 throttle lever position, part) 0 &lt; (A:Turb eng1 N2, percent) 1 &gt; and if{ (A:Turb eng1 N2, percent) 1 + (&gt;A:Turb eng1 N2, percent) } els{ l0 }</Value>

 

[jx_]

you can delete the airfile entry. It is overwritten by the -0.xx value. But it is the same variable.

Shorten 1505 by 100-200 in the slow spool segments.


Just curious, is 93% reverse approved for normal use on the VC10? Sounds like emergency thrust to me. Also, most (present day) reversers cannot be deployed until the engine has spooled down close to idle. Is that something they do differently on the Conway?

 

[vololiberista]

Hi JX,
Yes, today I'll have a go at tweaking the 1505 a little more.

The Conway is indeed a very robust engine. To quote from the "Engine Limitations"

Reverse thrust
Conway 540 "Standard VC10"
N2 94.5% N1 98% Max EGT 530

Conway 530B "Super VC10"
N2 93% N1 102% Max EGT 525
See Note 4

Note 4: Engines should not be operated continuously in reverse thrust for more than 30 seconds. The n2 is physically limited to a nominal 93% to prevent tailplane oscilations.
F2 or equivalent button on one's control column pressed once will give idle reverse. (One had better check the rwy length!!) held down will wind the engines up to full reverse.

The original code was quite confusing

<Value>(A:Turb eng1 N2, percent) s0 (A:General eng1 throttle lever position, part) [COLOR="Red"]0 &lt;[/COLOR] [COLOR="Blue"]if{ l0 10 + }[/COLOR] els{ l0 }</Value>

<Tooltip>Engine 1 %((A:Turb eng1 N2, percent) near)%!d!%%</Tooltip>

The bit in red made the gauges jump into life even with the engines off!!
I never could understand the bit in blue. Except that there was a discrepancy between the needle and the text. I decided to "force" the needl to 93% and in so doing discovered that the tooltip value was actually the correct number. So after that it was a case of finding the setting that produced a tooltip value of 93% and then as shown in an earlier post just making the needle follow.
Now as long as my throttle is closed the reverse works perfectly with even the correct pitch of compressor sound.
In practice one would never let n1 run down to idle before reversing as it would take the whole airport to get it back up to useable thrust! Plus the EGT would overshoot whilst waiting for n1 to get back up to speed.
Closing the throttle for the landing flare the engines are down to about 65%n2 on touchdown which means n1 is still high enoughto rapidly produce the necessary thrust and importantly produce cooling air (which I've also modelled) thus keeping EGT values within limits.
vololiberista

PS I forgot to mention that the VC10 has only 2 reversers. Originally four but cut because of tailplane oscilation. Hence 93%n2 on the remaining two.
Modern jets with their huge fans would work differently as they produce most of the thrust.

 

[Roy Holmes]

Your "bit in blue" is a good example of the tiny difference in appearance between

l0

which is "ell 0" or load 0 and

10

which is "one zero" or ten.
It is confusing and you need to look carefully at the adjoining code to see what the font is up to.

lever

starts with "ell"

eng1

ends with "one"

Each font seems to do it differently

BTW in your 7 Jan post you had

if{ (A:Turb eng1 N2, percent) 1 + (>A:Turb eng1 N2, percent) } els{ l0 }

You know you can not write to "read only" A:Vars using XML, so this bit does nothing, which I believe means the whole expression leaves you with the value (A:Turb eng1 N2, percent)

Roy

 

[vololiberista]

Hi Roy,
Yes I had noticed the difference between I0 and 10 !! And it may indeed have contributed to some of the original problems.
As for if{ (A:Turb eng1 N2, percent) 1 + (>A:Turb eng1 N2, percent) } Yes it's politically incorrect, but it does seem to have an affect. For one when I select reverse the reverse kicks in from wherever n2 happens to be instead of running down to idle first. Also the run up to 93% before was almost instant and this seems to keep it under control.
Either way correct or not it's the first time this model has had correct reverse numbers. Spooling up correctly and with the correct compressor sound. It was a joke before.
I'll play with your suggestion and see if there's any difference.
vololiberista

 

[jx_]

This code:

<Value>(A:Turb eng1 N2, percent) s0 (A:General eng1 throttle lever position, part) 0 &lt; if{ l0 10 + } els{ l0 }</Value>

Does absolutely nothing!! You could completely delete this and there would be no change.

In English:

Store Eng1 N2 to memory location Store0

If Throttle 1 position is less than 0, execute { Look up value of location Store0 + 10 }

Else, { Look up value of location Store0 }

Nothing is executed or implemented whatsoever. You need to input a command back into the sim variables to get something done. If you're getting good numbers it is because of the changes you made to the airfile and cfg.


If you want the Reversers to move faster in reverse that would be something like;

<Value>

(A:General eng1 throttle lever position, percent) 0 &lt;
if{ (A:General eng1 throttle lever position, percent) 163.83 * X - (&gt;K:THROTTLE1_SET) }

(A:General eng2 throttle lever position, percent) 0 &lt;
if{ (A:General eng2 throttle lever position, percent) 163.83 * X - (&gt;K:THROTTLE2_SET) }

</Value>

In English:

If Throttle 1 position is less than 0, { Increase current NEGATIVE throttle1 by X }

If Throttle 2 position is less than 0, { Increase current NEGATIVE throttle2 by X }

Replace X with a number where:

X = (Desired percent of throttle change per second in decimal format * 16383) / Gauge update rate.


Gauge update rate is found under <Update Frequency="8"/>. If it is missing, the MSFS default is 18.

So if we want the throttle lever to decrease (increase reverse) by ten percent lever per second:

X = (Desired percent of throttle change per second in decimal format * 16383) / Gauge update rate.
X = (0.10 * 16383) / 18
X = 91


If you want the Reversers to immediately go full reverse that would be;

<Value>

(A:General eng1 throttle lever position, percent) 0 &lt;
if{ -16383 (&gt;K:THROTTLE1_SET) }

(A:General eng2 throttle lever position, percent) 0 &lt;
if{ -16383 (&gt;K:THROTTLE2_SET) }

</Value>


In both cases you will be unable to control reverse manually and will be locked out of the throttles until setting idle forward.

 

[vololiberista]

You've given me some more ideas JX

<Value>(A:Turb eng1 N2, percent) s0 (A:General eng1 throttle lever position, part) 0 &lt; if{ l0 10 + } els{ l0 }</Value>

That was the original code that came with the a/c. It was never right and bugged me for centuries. Especially being able to fire up reverse with "dead" engines!!

I'm getting "acceptable" results with the new code more or less. But, I'll try out your ideas this coming weekend.

Yesterday I did some ground runs and a few take-offs from SLLP "El Alto" Bolivia 4,058mt elevation!! with the SVC10 with the new n1s and n2's also testing EGT and P7. Everything came within the "Engine Limitations" schedule. I was just outside the limits when doing the same from Kuwait Intl (Summer 54c!!) The procedure for a very hot airfield is not to stay on the ground for long as the ambient temp limit is actually 50c. In theory I suppose one could "factor" in "waiting around" time but nobody would notice I think!!!
vololiberista

 

[jx_]

That was the original code that came with the a/c. It was never right and bugged me for centuries. Especially being able to fire up reverse with "dead" engines!!

That code wasn't causing that problem. It doesn't send any instructions to the sim. All it does is reads a value from memory, but doesn't do anything with it. It couldn't affect your engines. The reverse issue you had is more than likely the one that is common, where your table 1506 has thrust at very low Cn1 and mach.

The problem is the sim reads an ambient headwind component of 5 knots as mach 0.0075 at sea level.

It would then interpolate CN1 and look up the thrust at Mach 0.0075 (even while engines are off). The thrust is produced even though there is no combustion.

This effect is compounded by the ram drag settings in table 1507. They are always active as well (which is correct, ram drag is present even while parked if there is ambient wind.) The problem here is Ram Drag was confused by MSFS to be only momentum drag, and they used thrust to implement it.


Stores like "s0" are used to reduce the need for repetitive typing. If you want to use stores in your code it would be something like:

<Value> (Alane Altitude, feet) s6
l6 -2000 &lt; if{ 0 (&gt;L:ALTITUDE_BLOCK,number) }
l6 0 &lt; l6 -2000 &gt;= &amp;&amp; if{ 1 (&gt;L:ALTITUDE_BLOCK,number) }
l6 1000 &lt; l6 0 &gt;= &amp;&amp; if{ 2 (&gt;L:ALTITUDE_BLOCK,number) }
l6 2000 &lt; l6 1000 &gt;= &amp;&amp; if{ 3 (&gt;L:ALTITUDE_BLOCK,number) }
l6 3000 &lt; l6 2000 &gt;= &amp;&amp; if{ 4 (&gt;L:ALTITUDE_BLOCK,number) }
l6 4000 &lt; l6 3000 &gt;= &amp;&amp; if{ 5 (&gt;L:ALTITUDE_BLOCK,number) }
l6 5000 &lt; l6 4000 &gt;= &amp;&amp; if{ 6 (&gt;L:ALTITUDE_BLOCK,number) }
.......
.......
</Value>


Here it uses the store to store (Alane Altitude, feet) into l6, then calls l6 over and over to make comparisons for the if{}.

When the if{} criteria is met, the number inside the if{} is set to L:ALTITUDE_BLOCK variable for use somewhere else. Only one comparison should be valid at a time, so the l6 comparisons need to be written carefully.

 

[vololiberista]

Hi JX,
I did cure the problem of reverse with the engines off some time ago by adding
(A:Turb eng1 N2, percent) 1 &gt; and

But since then as you've seen the code has been changed further.
You may be interested to know that your earlier suggestions have produced an unpredicted result. That is the spool-up time to 93%n2 in reverse is the same in every case and is exactly equal to the "forward" spool-up time. So it must I assume be following the 1505 table.
vololiberista