Brakes a bit ineffective?

Which engine is simulated?... is it the F110-GE-129?

Which engine is simulated?... is it the F110-GE-129?

 

 

yes, F-110-GE-129 according to F-16C e-shop page

yes, F-110-GE-129 according to F-16C e-shop page

Thank you sir! :thumbup:

The brakes and stopping distance seem fine to me.

Same here.

 

Damn ... never trust a feeling.

 

I've made a quick test tonight ... but I am not 100% confident on pram used for computation of refusal speed.

I will post my procedure tomorrow and see if/what I've made wrong.

 

It was just a quick test using the Instant Mission "Takeoff" ... and it wasn't successful (maybe better creating a dedicated flight for such as test?).

 

But first, few questions:

 

 

 

 

1 - The wind given on Briefing page, is the wind direction displayed on weather data where the wind goes ? ... or the bearing => direction where the wind comes from ? (as I would expect in an aero weather report ?

I am asking because report shows a wind : 135° @ 2m/s (4kts) ... but my a/c is initialized on RWY 31 (with 2m/s tail wind then?!)

 

2 - Any ways to ask ATC for the wind? (there is no wind sock on this airport I think).

 

 

 

3 - What is exactly the distance given in Airfield data on Map info (F10) -> Is it supposed to includes overruns?

 

 

4 - Do you confirm that runway length is in ft ... not in meter!? (7842m ... mmm ... I don think it is meter)

 

5 - Elevation ... in ft also right? ... not in meter as showed on the Airdrome data window... (altimeter show 1500ft, Google Earth shoes 1450ft ... so I've considered ft ... it makes sens but I prefer asking if there is not something I don't know).

 

I will explain my results later on once I am sure I took the right distances values, wind and temperature for calculation of refusal speed ...

 

Cheers!

 

PS: I love the ejection sequence!

Damn ... never trust a feeling.

 

I've made a quick test tonight ... but I am not 100% confident on pram used for computation of refusal speed.

I will post my procedure tomorrow and see if/what I've made wrong.

 

It was just a quick test using the Instant Mission "Takeoff" ... and it wasn't successful (maybe better creating a dedicated flight for such as test?).

 

But first, few questions:

 

 

 

 

1 - The wind given on Briefing page, is the wind direction displayed on weather data where the wind goes ? ... or the bearing => direction where the wind comes from ? (as I would expect in an aero weather report ?

I am asking because report shows a wind : 135° @ 2m/s (4kts) ... but my a/c is initialized on RWY 31 (with 2m/s tail wind then?!)

 

2 - Any ways to ask ATC for the wind? (there is no wind sock on this airport I think).

 

 

 

3 - What is exactly the distance given in Airfield data on Map info (F10) -> Is it supposed to includes overruns?

 

 

4 - Do you confirm that runway length is in ft ... not in meter!? (7842m ... mmm ... I don think it is meter)

 

5 - Elevation ... in ft also right? ... not in meter as showed on the Airdrome data window... (altimeter show 1500ft, Google Earth shoes 1450ft ... so I've considered ft ... it makes sens but I prefer asking if there is not something I don't know).

 

I will explain my results later on once I am sure I took the right distances values, wind and temperature for calculation of refusal speed ...

 

Cheers!

 

PS: I love the ejection sequence!

 

1. Make a simple mission in the ME with no wind - Tables use zero wind/slope.

2. See 1 above.

3. Generally the standard runway surface not including overruns. Use a standard runway - see 1 above.

4. Runway length is reported in Feet.

5. Irrelevant - just use a Caucasus airfield at sea level - see 1 above.

 

Why are you calculating refusal speed? Your refusal speed just says you 'should' be able to abort a take-off safely below this speed. Not that 'exactly' at that speed you will perfectly pull to a halt in the last foot of the remaining runway.

 

You might like to focus more on calculating Short Field Landing Distance - bit more relevant.

SB - Open

13 Deg AOA

Zero Wind/Slope

Idle throttle

Max Effort braking

Dry concrete runway - DCS Runway Condition Report (RCR) values may vary from standard - which makes a big difference!

 

Calculate Corrected Ground Roll Distance - simple calculation that we used to find on the fly in the seat at the last minute when the pilot wanted warm fuzzy feelings that we would be able to stop, no big deal and should be easy to do.

Edited December 5, 2019 by VampireNZ

Thank you for reply.

 

Refusal just because I takeoff before landing ;) ... indeed, it is not good to test only the brakes because any trust deviation will also have a big effect on results. But is it also interesting to check it and see if I can use still my old checklist ...

 

Hope to be able to dig it further tonight. I will also investigate a bit more on (1) and try to understand wind given in weather report since I am not always the mission designer.

 

Thank you again.

hi DJ, you can use the ruler function within the ME as well as the ingame map to measure distance (and bearing). maybe handy to quantify your accelerate-stop-distance or landing distance.

 

cheers

Have you thought about using time scale of 1/2 or 1/4 so you can do some very comparable and precise action on same speeds?

Haven't tested lately, but the main problem is that there's no difference in stopping distance with antiskid on and off, which doesn't make any sense.

Like with the F/A-18, antiskid on brakes are approx 30% too weak and I don't understand why ED considers the F/A-18 and F-16 brakes to be ok.

hi DJ, you can use the ruler function within the ME as well as the ingame map to measure distance (and bearing).

cheers

 

Yep sure , that is what I did.

But I was a bit confused by the "Airdrome Info" about runway length ... Now I understand: runway length given is not the real/full (available) runway length as the one published on Jeppsen or DOD publications but the distance between center threshold markings or QFU markings.

 

On QFU13 ASDA is rather 8846ft (less on QFU31):

 

 

maybe handy to quantify your accelerate-stop-distance or landing distance.

Actually, I didn't wanted to quantify a precise distance. To start with, I just wished to know if I can stop the a/c before runway end by initiating the abort takeoff procedure at the calculated refusal speed.

For ppl who have the supplemental or checklists, here is the parm I used to calculate the refusal:

 

For ppl how has what they need to check on their side, here is the param I considered:

 

(running on the DCSW Stable 2.5 version)

 

Engine: F110-GE-129

GW: 27400lbs (Empty configuration)

Runway Elevation: 1500ft

ASDA: 7842ft

QNH: 29.92

Temp: 10°C (50°F)

Wind 135°@4kts

Runway slope: 0%

RCR 23 (Runway dry)

Full AB

 

 

Takeoff Factor => 1.5

Refusal Speed => 180kts

 

Refusal speed based on:

- Zero taxi energy

- No braking above max brake application speed*.

- Brakes applied 3 seconds after idle selected.

 

*180kts near the max application speed for that weight within those conditions. But I don't now if Brake Energy Limits is implemented yet in "DCS F-16" ... (easy to check => Hot Brake => Later)

 

So for the test, I start from the very beginning of the runway so I have a little bit more margin in distance.

Apply 90%, brake release, engaging AB ... at refusal speed,

 

- Throttle Idle

- Air-brakes full extensions (overriding the 43°)

- Maximum effort braking

- No elevator inputs

 

Here is the track (.trk) for results : https://www.dropbox.com/s/5u99r4bf7x03pz9/Acc-Stop%20distance%20check.rar?dl=0

 

...

 

This test do not demonstrate that braking effect is accurate or not because thrust model deviation would modify the distance to reach the refusal speed and so the distance remaining for a/c to full stop.

 

It just shows that real charts can't be used (yet) to calculate the refusal speed in those conditions (maybe it works at higher GW?), and demonstrate (if my calculation and procedures are corrects) that something is not accurate, either in braking effect, or in engine thrust, or tires frictions ...

 

I don't think it worth to dig further yet. Maybe better wait further updates.

 

However, what Tom Kazansky said is right: "You might like to focus more on calculating Short Field Landing Distance - bit more relevant."

 

Much more relevant indeed for breaking effect tests.

 

Maybe tonight ... it is fun to play the test pilot (awaiting more combat functionalities). :pilotfly:

 

(Who said that we can't enjoy an EA? ... I have to confess that I changed my mind :music_whistling: ;) ... lot of fun indeed! :yes:)

 

Have you thought about using time scale of 1/2 or 1/4 so you can do some very comparable and precise action on same speeds?

 

Not a bad idea ... I will consider it! good hint! ... but results are so off that I don't need to be that much precise on that one. Maybe later.

 

Haven't tested lately, but the main problem is that there's no difference in stopping distance with antiskid on and off, which doesn't make any sense.

 

Is the Anti-Skid implemented yet (?). F-16 is still big WIP.

 

...

 

See ya later!

 

Cheers!

Edited December 5, 2019 by Dee-Jay

btw.: the "m" in F10 map at elevation of Vaziani is uncorrect too, according to wikipedia.

 

 

should be feet too.

 

 

and: thanks for your efforts to sort those things out

Edited December 5, 2019 by Tom Kazansky

btw.: the "m" in F10 map at elevation of Vaziani is uncorrect too, according to wikipedia. should be feet too.

 

 

Yeah ... it is obvious on Google Earth also https://www.google.com/maps?ll=41.62825,45.03294&z=14&t=h

 

 

 

m vs ft in Airport Info ... are they known issues? (Existing bug reports? I guess yes!)

Been landing the Viper and its a bugger to stop her from running off the end of the runway! I'm finding the wheel brakes need a little more power..

 

Am I the only one?

 

 

Confirmed.

Brake efficiently is very far from nominal.

I personally don't understands ED's aversion to using actual performance data from the appropriate flight manual that has been determined by the aircraft manufacturer - preferring to use the SME 'she'll be right' approach.

 

Surely you realise ED aren't going to model the Viper's stopping distance directly?

The main issue is anti-skid. The wheels lock up and skid with anti skid on in both the Hornet and Viper.

The Hornet stops real good on the boat. :)

Hi gents!

 

Yesterday evening tests on a light aircraft on Batumi airfield ... at seal level, STD atmosphere, no wind, empty a/c.

 

 

Measured ASDA : 7780ft (for some reasons Airdrome info is not reliable?)

Two Airshow cones positioned at 2000ft from brake release point for acceleration check.

 

Test protocol conformal (see *) to checklist/supplemental data and procedure

 

- Idle at calculated Refusal Speed.

- Full air-brakes

- Max energy braking *

- No elevator inputs

 

* Only deviation is that I won't wait 3s between idle set and brake action.

 

I will apply the brake immediately after setting idle which should save about 660ft or stop distance, theoretically, a/c should stop about 660ft (200m) before the end of the runway.

 

 

Two tests performed: Track files => Acc-Stop Distance Tests.rar

 

- Without AfterBurner calculated parameters:

 

F-16 Blk 50 F110-GE-129

GW : 27400 lbs Runway

ASDA : 7780 ft

Elevation : 0ft

QHN : 29.92 inHg

Temperature : 15°C (50°F)

Wind Clam RCR : 23 (Dry runway)

- Takeoff Factor (Non AB) : 2.4

- Refusal Speed (Non AB) : 175 kts

- Takeoff Speed : 153 kts

- Takeoff Distance : 2400 ft (Non AB)

- Acceleration Check Speed (Non AB) : 144 kts (@ 2000ft dist from brake release).

 

 

 

- Acceleration check:

Passing the 2000 ft I read 162 kts for 144 kts calculated.

 

- Acceleration-Stop distance:

Passing EOR I still have about 100 kts.

 

A/C can't be safely stopped on the runway => ejection.

 

 

 

 

 

- With AfterBurner calculated parameters:

 

F-16 Blk 50 F110-GE-129

GW : 27400 lbs Runway

ASDA : 7780 ft

Elevation : 0ft

QHN : 29.92 inHg

Temperature : 15°C (50°F)

Wind Clam RCR : 23 (Dry runway)

- Takeoff Factor (AB) : 1.4

- Refusal Speed (AB) : 190 kts

- Takeoff Speed : 153 kts

- Takeoff Distance : 1300 ft (AB)

- Acceleration Check Speed (AB) : OFF SCALE (at least 190 kts)

 

 

 

- Acceleration check:

Passing the 2000 ft I read 195 kts ... conformal but chart do not allow to get a value at 2000ft ... we are off scale. A/c should already be airborne at this time with a 1300 ft takeoff distance.

 

- Acceleration-Stop distance:

Passing EOR I still have about 120 kts.

 

A/C can't be safely stopped on the runway => ejection.

 

...

 

With the Track Files, you will also find a .trk where rejected takeoff is initiated at calculated Takeoff Speed (153 kts).

Even much lower than theoretical refusal speed, a/c can't be stopped before EOR.

 

My conclusion are that acceleration is maybe not very accurate. (mostly with afterburner) but biggest delta with computed figures is the brakes efficiency.

 

Could in also interesting to make the same tests with an heavier GW and/or on a wet runway. ... But I am not sure it worth the effort yet. Better wait for further updates.

 

Of course, if you have any remarks about the test protocol, about my results and conclusions, please share your thoughts.

 

Regards.

Edited December 8, 2019 by Dee-Jay
Typo (Runway 7780 ft not m!) Acce check with AB conformal after a second check.

is Viper's v1 really that high?

is Viper's v1 really that high?

 

 

Nope. ;)

It is a computed maximum acceleration-stop speed which should ensure a/c stop within a given distance.

But here it's just a "flight test" ... we do not takeoff, otherwise a/c would be off ground at calculated takeoff speed (here it would be 153kts).

 

So at that gross weight (27400lbs) and with that runway length (ASDA 7780 ft), runway is not restrictive, and there is no V1 ... or you can also say, V1 equals to the takeoff speed => actually, at the rotation* speed to be more precise, so:

 

153 - 15 = 138 kts (for AB T/O)

153 - 10 = 143 kts (for Non AB T/O)

 

 

*ROTATE AT 10 KNOTS LESS THAN COMPUTED TAKEOFF SPEED FOR NON-AB.

*ROTATE AT 15 KNOTS LESS THAN COMPUTED TAKEOFF SPEED FOR AB.

 

But in both cases, ASDA will not be restrictive since rotation speed is way below the max refusal.

 

Hope I am clear (?)

 

 

EDIT:

Of course, it will be way different at Max Takeoff weight on a higher temperature and shorter runway.

Edited December 6, 2019 by Dee-Jay

I guess so.

 

 

Has any SME at ED checked such a rejected take off? Could be very interesting.

Brakes a bit ineffective?

 

Dee-Jay, so by your testing your conclusions are that the problem isn’t just the lack of brake energy. It’s also a surplus of power plant energy or lack of drag/friction?

 

(I guess friction is brake energy, but I’m thinking more of induced drag)

 

Sent from my iPhone using Tapatalk Pro

Hi!

 

Dee-Jay, so by your testing your conclusions are that the problem isn’t just the lack of brake energy. It’s also a surplus of power plant energy or lack of drag/friction?

 

I don't really know. Again, I'm just pilot, not engineer. :happy:

 

IMO, thrust is rather alright (at least at that GW, on ground in STD ATM). Yes we have 20kts more at Non AB acc check, but ... this is not that much off (162 vs 144kts ≈ +12% ) But only one test in single condition is not enough to tell you more.

 

Lack of friction? ... That is possible also. Maybe a bit of all you've mentioned (?)

 

I may have a look next Stable update, or maybe, will take a look to other things if time permit (quite busy on other areas, I was just taking a pause to fly DCS a bit more and something different than UH-1 :punk: ) ... but from that point, better wait for ED's SMEs inputs.

 

Cheers! Happy flying! :bye_2:

Edited December 6, 2019 by Dee-Jay

Hi!

 

 

 

I don't really know. Again, I'm just pilot, not engineer. :happy:

 

IMO, thrust is rather alright (at least at that GW, on ground in STD ATM). Yes we have 20kts more at Non AB acc check, but ... this is not that much off (162 vs 144kts ≈ +12% ) But only one test in single condition is not enough to tell you more.

 

Lack of friction? ... That is possible also. Maybe a bit of all you've mentioned (?)

 

I may have a look next Stable update, or maybe, will take a look to other things if time permit (quite busy on other areas, I was just taking a pause to fly DCS a bit more and something different than UH-1 :punk: ) ... but from that point, better wait for ED's SMEs inputs.

 

Cheers! Happy flying! :bye_2:

 

 

 

No, no, it’s all good. Just appreciate you doing that. I’m not caught off guard by the results not completely matching the 1-1, but the excess speed combined with the lack of braking energy may be a combined result why the accelerate-stop calculations don’t match. Anyways, EA. Good day!

 

 

Sent from my iPhone using Tapatalk Pro

is Viper's v1 really that high?

 

Are you thinking V1 as in an airliner? If so, some info that might help:

 

Airliners normally operate with reduced thrust on takeoff, based on a 'balanced field'. In this case, V1 is calculated so that upon reaching said speed, the runway remaining is sufficient to stop on the runway should you abort, but also the same distance to continue to accelerate and get airborne following an engine failure. V1 is therefore a single figure.

 

The viper is of course single engine, and doesn't takeoff on with reduced thrust. The additional acceleration means for a given speed, there's much more runway available to stop on than an airliner. This means it can be going much faster and still be able to stop, hence the higher abort speed. I think :book:

Are you thinking V1 as in an airliner? If so, some info that might help:

 

Airliners normally operate with reduced thrust on takeoff, based on a 'balanced field'. In this case, V1 is calculated so that upon reaching said speed, the runway remaining is sufficient to stop on the runway should you abort, but also the same distance to continue to accelerate and get airborne following an engine failure. V1 is therefore a single figure.

 

The viper is of course single engine, and doesn't takeoff on with reduced thrust. The additional acceleration means for a given speed, there's much more runway available to stop on than an airliner. This means it can be going much faster and still be able to stop, hence the higher abort speed. I think :book:

 

 

Makes sense. Thanks