Approach Speed/AoA too high

[Get_Lo]

F1 feels like it lacks lift, especially on the low speed ranges near300Knts, I decided to run a landing test to see if the performance lined up with the manual.
Conditions:
Clean, 20% fuel, 8700kg at the start of final approach, no wind.
Manual details regarding approach:

Cockpit readings on landing approach:

Tacview true AoA: 

Track file attached below. As we can see the F1 (even under 8700kg) is requiring too much AoA to land at the speeds it is designed to land at. AoA gauge in the cockpit is reading about 7(!) units higher than what the manual states is required to be held. This lack of lift really makes takeoff and landing distance more than it should be as well as more dangerous if we are trying to fly the conditions the manual recommends. This lack of lift also reflects on the energy retention and turn rate in a dogfight, making it worse than it probably was in reality.

Mirage_F1_Landing_Showcase_at_20_Fuel.trk

Edited August 1, 2022 by Get_Lo

[gnomechild]

The touchdown AoA is for flare out isn't it? Are you testing it with that in mind? So far I've not had any discrepancies between speed and AoA for a given weight in terms of all green. Gear down + flaps down at the same weight I can hold 10 degrees of incidence at nearly exactly 150kts. Seems odd if it would diverge by that large of an amount right at the end. You may be accounting for this in your test, or maybe it doesn't matter and I'm thinking of it wrong. Just wondering if that might be part of the issue that the AoA/speed maybe is not meant to be sustained but rather just a guide for flaring out? 

[Get_Lo]

3 hours ago, gnomechild said:

The touchdown AoA is for flare out isn't it? Are you testing it with that in mind? So far I've not had any discrepancies between speed and AoA for a given weight in terms of all green. Gear down + flaps down at the same weight I can hold 10 degrees of incidence at nearly exactly 150kts. Seems odd if it would diverge by that large of an amount right at the end. You may be accounting for this in your test, or maybe it doesn't matter and I'm thinking of it wrong. Just wondering if that might be part of the issue that the AoA/speed maybe is not meant to be sustained but rather just a guide for flaring out? 

Indeed it is for a "flare out" but not as much as you would think, the flare only brings the nose AoA up 2 more units as stated in the manual, where as in DCS in order to hold the same speed specified in said manual we need to bring the nose up about 7 more units, which needless to say is A LOT. as for a more aggressive flare to maintain the speed easier this would be possible but it would only make the issue worse as our AoA meter would be reading off the charts to maintain a sink rate that wouldnt explode the jet on touchdown. as for 150knots I do agree it feels better, the issue seems to compound the further down you go with the first affects being noticed at about 400knots in a turn. and as for sustaining this AoA, it is not sustainable. as you can see the F1 is on a very normal glide slope and any attempt at maintaining this flight condition in level flight even in ground affect results in the AoA meter being off the charts followed shortly by the jet falling out of the sky.

To simply for anyone wanting to test, at 8700kg (20% fuel clean) the plane should be able to fly a 2.5deg glideslope at 150knots and decelerate down to 136 knots before touchdown while not exceeding 13 units of AoA.

Edited August 1, 2022 by Get_Lo

[sedenion]

I did not made rigorous testings, but I also find the aircraft hard to land. Either you touch the ground hard way, or you touch at high speed and have hard time to stop before the end of runway.

Edited August 2, 2022 by sedenion

[felixx75]

I have no problems landing the F1. Like in the M2000C you have markers for a 3° glideslope (and 6°). Just align this marker with your flight path marker and the correct AoA. It's not that difficult.

[Get_Lo]

Just now, felixx75 said:

I have no problems landing the F1. Like in the M2000C you have markers for a 3° glideslope (and 6°). Just align this marker with your flight path marker and the correct AoA. It's not that difficult.

No one is saying its impossible to land, im saying it needs to land a bit fast to match the correct AoA and glideslope, did you even read the original post?

[felixx75]

"Sedenion" said, it's hard to land.

"Either you touch the ground hard way, or you touch at high speed and have hard time to stop before the end of runway."

But if you use the given markes, it's quite easy to land it smoothly (with a little bit of practice).

Edited August 2, 2022 by felixx75

[Get_Lo]

Just now, felixx75 said:

"Sedenion" said, it's hard to land.

"Either you touch the ground hard way, or you touch at high speed and have hard time to stop before the end of runway."

But if you use the given markes, it's quite easy to land it smoothly (with a little bit of practice).

 

well if you read the manual and think thats how its actually going to work and you fly that approach, yes its hard to land. but after some practice you can land it nice and smooth, you just have to be going 10-15 knots faster than normal. which is the whole point of this bug report.

[sedenion]

13 minutes ago, felixx75 said:

I have no problems landing the F1. Like in the M2000C you have markers for a 3° glideslope (and 6°). Just align this marker with your flight path marker and the correct AoA. It's not that difficult.

The 2000 is way easier to land... especially since the latest updates (where it finally land like it should). But the comparison has something correct, since the current F1 landing remind me landing with the first versions of the 2000... the aircraft feel "heavy".

Edited August 2, 2022 by sedenion

[felixx75]

16 minutes ago, Get_Lo said:

well if you read the manual and think thats how its actually going to work and you fly that approach, yes its hard to land. but after some practice you can land it nice and smooth, you just have to be going 10-15 knots faster than normal. which is the whole point of this bug report.

I don't look at the speed, I look at the AoA, glideslope marker (3°) and the flight path marker. The speed results from this automatically. If this speed is higher or lower, than the manual says, ok. But the differences are not really big (for me lower than 10-15 knots)...

[Get_Lo]

6 minutes ago, felixx75 said:

I don't look at the speed, I look at the AoA, glideslope marker (3°) and the flight path marker. The speed results from this automatically. If this speed is higher or lower, than the manual says, ok. But the differences are not really big (for me lower than 10-15 knots)...

just because the problem can be ignored/avoided doesnt make it not a problem. Jet was designed to land at 135knots at 13 units AOA, manual says I should be able to land at 135knots at 13 units AOA, I want to be able to land at 135knots at 13 units AOA. This bug report is about more than just landing comfort. lift has to do with your stall speeds, your takeoff runs, your ability to dogfight, and your ability to get out of trouble, climb, and pull out of dives. landing is probably the least of these concerns but its the easiest metric to measure to show the issue. 

Edited August 2, 2022 by Get_Lo

[sedenion]

The fact is that it is hard to land bellow 150kt with ~25% fuel... I managed to land around 160kt/11° AOA and that was not a soft landing, another try around 150kt/13° AOA and hitting the ground quite hardly...

Edited August 2, 2022 by sedenion

[gnomechild]

4 hours ago, Get_Lo said:

just because the problem can be ignored/avoided doesnt make it not a problem. Jet was designed to land at 135knots at 13 units AOA, manual says I should be able to land at 135knots at 13 units AOA, I want to be able to land at 135knots at 13 units AOA. This bug report is about more than just landing comfort. lift has to do with your stall speeds, your takeoff runs, your ability to dogfight, and your ability to get out of trouble, climb, and pull out of dives. landing is probably the least of these concerns but its the easiest metric to measure to show the issue. 

 

Hmm now that you've mentioned it, the takeoff run does seem to be longer than it should. The plane is kind of "stuck" to the runway and even though you can rotate at 120 in a clean + magics loadout, it doesn't come off the tarmac for another 20-30 kts. It's quite difficult to get the gear up on time following the schedule in the manual. I almost always get a couple of warning tones before they're finished.

 

I initially just figured it's a "skill issue". But my last few take offs I've nailed the 12⁰ rotation pretty damn close and still am not getting positive rate on "schedule" for the aircraft weight 

Edited August 3, 2022 by gnomechild

[Get_Lo]

29 minutes ago, gnomechild said:

Hmm now that you've mentioned it, the takeoff run does seem to be longer than it should. The plane is kind of "stuck" to the runway and even though you can rotate at 120 in a clean + magics loadout, it doesn't come off the tarmac for another 20-30 kts. It's quite difficult to get the gear up on time following the schedule in the manual. I almost always get a couple of warning tones before they're finished.

 

I initially just figured it's a "skill issue". But my last few take offs I've nailed the 12⁰ rotation pretty damn close and still am not getting positive rate on "schedule" for the aircraft weight 

 

There are many skill issues to come across on these forums, but I assure you I and others have taken the time to assure that our tests and parameters are fair and accurate, we cross reference not only the Aerges manual but also other public data available about the jet. This issue originally came to my attention when doing an in-depth analysis of the aircraft's rate fighting abilities and noticed some unusual trends in the speed ranges below 400knots. The best way I figured I could get easily referenceable data on this would be a simple landing speed performance test, and the results seem to confirm my suspicions. if you would like to tag on any data regarding the takeoff performance that would be welcomed as well.

[sedenion]

8 hours ago, gnomechild said:

The plane is kind of "stuck" to the runway and even though you can rotate at 120 in a clean + magics loadout, it doesn't come off the tarmac for another 20-30 kts.

Yep, almost like the first versions of the 2000, like tearing out tape...

[jojo]

For landing…TBH I need to practice more too.

For the take off, I agree the nose is stuck down before 140-150kt even if light. But it’s early access.

[sedenion]

2 hours ago, jojo said:

For landing…TBH I need to practice more too.

For the take off, I agree the nose is stuck down before 140-150kt even if light. But it’s early access.

I notice thing... In this video it land with flaps full down, while what is called "Flaps Landing position" in controls corresponds to the intermediate position (and that's how I usually landed since now). The manual simply don't mention flaps... Some clarifications would be appreciable. Anyway, from my of view it still suspicious how touchy it is to land with 20% fuel and flap to intermediate position.

Edit: Retried with flaps full down, still hard to land bellow 150kts... flaps increase drag making the aircraft a little easier to stop, but it still heavy on touch down.

Edited August 3, 2022 by sedenion

[felixx75]

You're starting (and landing) the F1 with full flaps.

[jojo]

On 8/3/2022 at 6:55 PM, sedenion said:

I notice thing... In this video it land with flaps full down, while what is called "Flaps Landing position" in controls corresponds to the intermediate position (and that's how I usually landed since now). The manual simply don't mention flaps... Some clarifications would be appreciable. Anyway, from my of view it still suspicious how touchy it is to land with 20% fuel and flap to intermediate position.

Edit: Retried with flaps full down, still hard to land bellow 150kts... flaps increase drag making the aircraft a little easier to stop, but it still heavy on touch down.

 

Half flaps on take off only if you're slick.

Full flaps on landing.

[felixx75]

I just stick to the normal procedures "After Start" (point 4) for T/O, even if I'm slick  
Of course, I don't have a "real" F1 manual at hand, only the one that comes with the module. 

Edited August 5, 2022 by felixx75

[IvanK]

My 2C worth

F1 Vref

The Mirage F1 Approach speed  (Vref) in knots versus weight/ fuel remaining in litres for approach incidence 10deg indicated on AOA tape. All based on config below:

Full Flap, gear down, 2x R5550

Rpm to maintain 2.5 deg slope

DCS Jet fuel SG is 0.79

 

Tested 2 data points in game then extrapolated Vrefs. This compares closely with Flight manual data that plots 10deg Incidence versus weight. So to me what we see on approach in DCS is pretty close to the book numbers.

 

DCS VREF for 10deg Incidence versus Fuel remaining Weight.

 

Fuel rem      DCS Vref

500l            146k

1000l          150k* MLW      (Flight manual Vref 151k)

1500l          154k

2000l         158k

2500l         162k

3000l         166k

3500l         170k

4000l         174k.              (Flight manual Vref 176k)

4247l         176k               (Full internal fuel)

 

Rule of thumb : Vref increases by 4knots for every 500l of Fuel

 

Flight Manual Norm Maximum Landing Weight: 9000kg (1012l fuel rem.)*

Flight Manual Emerg Maximum Landing Weight: 11,000kg (3951l fuel rem)

So You shouldn’t be landing in most cases with more than 1000l fuel remaining.

Until I start the flare 10deg AOA is what I want to see.

Edited August 21, 2022 by IvanK

[pierrewind]

Using weight from the Loading window at 10 AOA my speed is reading about 165kts. I get about 152kts at 13 AOA.

Admitedly I haven't tested it in the perfect config (9P instead of 550)> I am still showing clearly higher speeds than expected.

I have no idea how can IvanK find his speeds...
Though there also seems to be a refuel weight bug... 

Mirage f1 speed test.trk

[IvanK]

I used the Mission Builder weight dialog as a starting point to determine Empty weight +R550's. I then slowly increased fuel % and noted the litres this equated to. This revealed the DCS Jet Fuel Specific Gravity (SG) of 0.79. So knowing the weight and the DCS SG you can now determine the aircraft weight for any Fuel amount.

I then took the values from the Flight manual for 10 deg AOA (Chart in first post of this thread). I then made sure I had the weight the same in the chart (by varying fuel loading) and then jumped in DCS and flew the approach exactly at 10 deg AOA at exactly 2.5 degree flight path angle and noted the resultant IAS at both 8700kg and 11,000kg. The IAS in both cases was in very close agreement with Flight Manual chart. The next step was to extrapolate to obtain the IAS for each Weight/fuel remaining value. I have subsequently flown at random Fuel weights and noted the relationship between AOA/IAS and Fuel weight is in very close agreement with the extrapolations.

Given there is no real time weight indication in the F1 the only way to do it accurately is by Fuel remaining and adding that to your Basic wt. Of course to be super accurate you need to make allowance for other configurations or expended stores. Doing the numbers here shows that a 100Kg change in wt is a 1Kt change in Vref at 10deg AOA

I did not use the Arming/Loading window at all.

The only value really required is for 10 Deg AOA as thats what you fly final at and how the APP mode in the sight is set up. 13deg AOA is irrelevant imo in this case... its something you see in the flare and its relevance is simply Tail strike awareness.

From a practical point of view I have found that initially in setting up the approach going for the speed (for fuel remaining) is easier than chasing the AOA. Once pretty close then refine and continue with the AOA. The relationship between the orange VV and the site approach reticle works just like an E bracket.

Edited August 22, 2022 by IvanK

[Get_Lo]

40 minutes ago, IvanK said:

I used the Mission Builder weight dialog as a starting point to determine Empty weight +R550's. I then slowly increased fuel % and noted the litres this equated to. This revealed the DCS Jet Fuel Specific Gravity (SG) of 0.79. So knowing the weight and the DCS SG you can now determine the aircraft weight for any Fuel amount.

I then took the values from the Flight manual for 10 deg AOA (Chart in first post of this thread). I then made sure I had the weight the same in the chart (by varying fuel loading) and then jumped in DCS and flew the approach exactly at 10 deg AOA at exactly 2.5 degree flight path angle and noted the resultant IAS at both 8700kg and 11,000kg. The IAS in both cases was in very close agreement with Flight Manual chart. The next step was to extrapolate to obtain the IAS for each Weight/fuel remaining value. I have subsequently flown at random Fuel weights and noted the relationship between AOA/IAS and Fuel weight is in very close agreement with the extrapolations.

Given there is no real time weight indication in the F1 the only way to do it accurately is by Fuel remaining and adding that to your Basic wt. Of course to be super accurate you need to make allowance for other configurations or expended stores. Doing the numbers here shows that a 100Kg change in wt is a 1Kt change in Vref at 10deg AOA

I did not use the Arming/Loading window at all.

The only value really required is for 10 Deg AOA as thats what you fly final at and how the APP mode in the sight is set up. 13deg AOA is irrelevant imo in this case... its something you see in the flare and its relevance is simply Tail strike awareness.

From a practical point of view I have found that initially in setting up the approach going for the speed (for fuel remaining) is easier than chasing the AOA. Once pretty close then refine and continue with the AOA. The relationship between the orange VV and the site approach reticle works just like an E bracket.

 

Perhaps you can post us a video, because many many tests of my own doing and others gave yielded AoAs far higher than the manual would suggest.

[IvanK]

Here is My effort. Weight 8684Kg based on Fuel weight added to Mission builder displayed Weight. Wanted 8718Kg to align with Flight Manual data. Fuel burn during the test dropped it by 34Kg.

Flight Manual 10deg Incidence Vref 151Knots at 8700Kg , Stable trimmed On speed hands off at 10deg Incidence I get 152K-153Kias ... close enough for me.

Level Flight tests outside of ground Effect at 13 Deg incidence are not valid imo. AOA v IAS in ground effect (where you will be during the flare) will bear very different value.

Trk attached

F1Vref_8718kg.trk

Edited August 23, 2022 by IvanK