DCS F/A-18 questions

Hi, guys! I got a question for you, removing the pylons from the F/A-18 will increase maximum speed of several extra knots because of little less drag than the F/A-18 with the pylons on it? Thanks!

Cheers,

Vincent

so what is the question, since you have already answered your own question

Currently no, it's just a visual thing and it makes no difference to the flight model. However this may change in the future.

Hi, pete_auau! Zomba already answered my question! @Zomba: thanks!!

Cheers,

Vincent

On the f-18, Max speed is not related to pylon drag. It's related to air flow to the engine.

Max speed at sea level may be affected by pylons, but absolute max speed is limited by the lack of inlet control surfaces.

Air supersonic relative to the compressor face cannot be compressed by the engine, which is why aircraft like the f-15 and f-14 and sr-71 have moveable surfaces that control the shockwaves to make sure supersonic air decelerates (which adds a ton of "pre-compression" by the way, making less work for the engine). As speed increases, those shockwaves move inside the inlet and approach the compressor face... without moveable surfaces to control them, the f-18 engines, although powerful enough to accelerate it beyond mach 1.8, cannot be fed with air beyond that speed. No air compression = no thrust = limited speed. BAsically, supersonic air causes compressor stall, so you have to slow it down before it hits the front of the engine inside the inlet.

This explains with images and video (worth 1000 words):

Hi, guys! Question for you, do you know what is the F/A-18’s maximum IAS or vne before the F/A-18 will get structural damage? Thanks!

Cheers,

Vincent

Anybody here about the F/A-18’s vne in indicated airspeed? Thanks!

Cheers,

Vincent

On jets and turboprops there's usually no VNE and there's no reason why an aircraft should suffer from structural damage just by exceeding VNE/VMO.

VMO in the F/A-18 depends on altitude and varies between 720 and 780kcas. MMO is 2.0.

Hi, bbrz! That makes sense!! Thanks!!

Cheers,

Vincent

Question for you, when I go up to an altitude of 70,000 feet in the F/A-18 the altitude readout on the HUD stops going any higher than 70,000 feet! Any idea why is that? Thanks!

Cheers,

Vincent

Hi usmc trev! The backup altimeter rolling drum stop working when get up to 70,000 feet but the needle keeps turning!

Cheers,

Vincent

It all depends on where in the envelope you find yourself. Below 20,000-ish feet you are limited by KIAS, and with a lot of fighters it is limited by the canopy temperature. Above 20,000-ish feet you are Mach limited. Mach limitations are tricky, it could be choking a fixed inlet or it could be flutter limited, which is very configuration specific. Without specific information it is very difficult to make categorical statements.

FWIW one of the real world flight test techniques I've done many times in the BUFF was to set up at Vmo at 22-23 Kft and slowly descend until we hit Vne somewhere between 19-21 Kft. This was usually the most challenging condition for weapons releases.