LJQCN101

I'm so sorry sir, best regards to those people. :cry:

Thanks for the data. I can recall that last time when I was in a 31-ton-Su33 on final, the indicated optimal speed on HUD is 300KM/H. Check needed. BTW I'm from China. :D 31-ton-Su33 Carrier Landing Video Link: http://v.youku.com/v_show/id_XODA1NTY1Njg4.html (Filmed in LOFC2. Didn't own DCS:FC3)

Been went into an endless argument with one guy about the flight model currently adapted by Su-27. The guy keep stating that the Su-27 FM is currently an AFM. :doh: So I wanna reconfirm that the Su-27 in the lastest version of DCSW:FC3 is still using SFM, is that correct?

I was searching the forum for Su-33 carrier landing techniques along with some Youtube videos on this subject, that I noticed some people tend to land the aircraft with a higher landing speed than what is suggested by the HUD, usually with a flashing yellow light in the AoA indicator. I even succeeded in carrier landings with a speed as fast as 400 km/h. So, I wonder IRL, is there any potential danger or hazard in landing the aircraft faster than normal? (i.e. the optimal speed is 250 km/h in certain conditions but you're landing with a speed of 300.)

Nah..Just a reminder, or blathering cuz someone mentioned F-16, never mind.;) Good to hear what a real F-15 is like.

Well, the "high speed control losses" may be referred to as a "departure". A departure is a loss of aircraft control that is characterized primarily by uncommanded aircraft motions or failure of the aircraft to respond to control commands, and is very different from what we called a "stall". For instance. The critical AOA of an F-16 is 35°, and the aircraft stalls above critical AOA. At the same time the F-16 experiences a loss of efficiency of the elevator (and therefore a loss in nose down control effectiveness) when exceeding 25° AOA, which is called a pitch departure. The pitch FLCS prevents pitch departures and has nothing to do with stalls.

Watch your angle of attack carefully. In current version of DCS F-15C, roll departure is expected above 35 units AOA, together with a loss of roll control effectiveness.

That's called AOA buffet and starts at about 18~20 units AOA, when you'll experience a slight shake if you pay (a lot) attention to this. The AOA buffet increases in intensity to 23 units, then remains fairly constant. And 23 units AOA is far from critical AOA, which is 45 units in a F-15C.

Tested and finally confirmed: When the gear handle is positioned down, normal acceleration signals and the pitch rate canceller circuit are eliminated. Thanks for reminding NASA. Almost forgot.:D

Aerodynamic brake is used to slow the plane down after touch down (above 90 knots). It's more effective than a mere air brake.;)

Regarding the PTC: During my test, the pitching momentum induced by a prompt thrust increase/decrease will cause a 0.1g increase/decrease in load factor, and is compensated later on. And the g changes caused by speed brake is negligible. Well, I just observed in the game that the PTC does not attempt to keep the pitch rate. Without pilot input, the CAS commands a permanent normal acceleration of +1g. For example if you adjust your pitch to +40 degrees and maintain the airspeed, you'll find out that the nose of the aircraft gradually goes up, but the load factor remains at +1g. (Without pilot input) And that remains the same when your landing gear is down. The CAS still commands +1g without pilot input, until the AOA is a little bit high. Also observed a pitch-down when AOA approaches 18 units or higher when landing gear is down. Maybe there's a AOA feedback blended into the CAS, not quite sure for this one.

Really nice info, THX a lot. Maybe I'll pay more attention to the PIO, or intentionally induce it for testing purpose.;)

Sure. It isn't SOP to use it indeed. Just as you said: "as required". Good point. Then clarify it a little bit if you're more knowledgeable than us. We'll appreciate that. Especially the pitch issue. I thought the pitch CAS was a pitch rate command system when landing gear is down (g command when landing gear is up), and will automatically compensate for the pitch-down momentum induced by speed brake or thrust reduce, done by the Pitch Trim Compensator (PTC). Will dig-in more if I have proper info.

Search for "F-15 Eagle Landing Runway 03R HYAKURI AIR BASE" on YOUTUBE and what you're about to see is a full overhead landing procedure with speed brake ON all the way. The truth is, IRL there's no restrictions in deploying speed brake duiring normal landing. ${1} I tend to extend the speed brake from the downwing leg all the way to taxi, just as the video shows, and haven't seen any harzard or difficulties in using this technique. IIRC speed brake is also used to avoid a floating tendency when entering ground effect.

Totally agreed. It seems to me that the lack of a specific flight characteristic such as wing rock is a less concerning issue than what already exists. May be I'm too sensitive about handling quality and stability issues. For example duiring my test on pitch short period mode and dutch roll mode of the aircraft, I observed an abmormally high dampening momentum in both pitch and yaw axis no matter CAS is on or off. But that's easy to fix I think, and hopefully we'll see a pretty satisfying PFM at last. :thumbup:

Landing approach speed for F-15C with F100-PW-220 engine: Remember to fly 22 units AOA (max) and a 2.5°~3° glide-path. Source: T.O. 1F-15A-1

Yeah, it seems that spin resistance of the aircraft has been enhanced. And that's good improvement because IRL F-15C is quite resistant to spins except above 20000Ft and with large asymmetric loads. A centerline tank will further aggravate the susceptibility to spin. Will test that later.

As for the spin recovery technique in real life F-15C. Under high AOA conditions, rudder is less effective in creating yaw moment (Cn, aka Yawing momentum) than ailerons. For example: In normal conditions, a left rudder input will make the nose of the aircraft slice to the left. However in high AOA regions, to make the nose slice to the left, rudder input is ineffective. To many people's surprise, a right stick input will make it. Yeah, in the opposite direction. And that phenomenon is called "Adverse Yaw". So in real life, the proper spin recovery technique in a F-15C is, as proposed by T.O. 1F-15A-1, full lateral stick in the direction of spin. Rudder is useless. As opposed to what is suggested in the DCS F-15C manual. And you're right, opposite roll input while in a spin does aggravate the spin.

I've been testing the F-15C PFM for a period of time, got some really strange feeling in terms of pitch short period mode, dutch roll mode, inertia-coupling, departure/spin characteristics, etc.. So I wanna start with some simple flight characteristics such as 1G stall, and compare it to the description in the real life manual. (Reference manual: T.O. 1F-15A-1) Here's the video link :http://v.youku.com/v_show/id_XNzUzMTc5MzA4 As one can see, the AOA buffet is modelled quite well. Wing rock and yaw oscillation are not observable. And the worst part, I can't pull the aircraft above 38 units AOA, let alone to stabilize at 45 units. The aircraft just went roll departure everytime when reaching 35 units AOA, which reveals a poor departure resistance. Here's a departure/spin susceptibility summary of a real life F-15. If it were me to fill in the blanks for DCS F-15C, I won't give any words similar to "Resistant". So what is called "Resistant" then? In December 1979, the NASA Langley Research Center conducted a study on stall/post-stall characteristics of a real-time simulated fighter. During the test, the control system is modified to decrease the susceptibility to departures while not degrading maneuverbility and control response. There're Basic Control System, which has least anti-departure ability; Control System B, and Control System C. Finally in Control System C, with full lateral stick input applied at 0.6Mach and an altitude of 9144m, followed by a full nose-up pitch command, the control system effectively handled the aircraft during the whole 11-sec-test so that there're no pitch/roll departure occured compared to the Basic Control System. And that is called "Resistant". With such departure susceptibility as in DCS F-15C, I wonder if it represents the real one, will it even be approved to put into production.