Commander Naval Air Forces wants more F/A-18s

[35_aoa]

Are speedbrakes back for the BLOCK III Super Hornet or are the big slabs something else?

I might be misinterpreting your question here, but the E/F/G has always had those two "spoilers" (shown extended in the pic). They work in conjunction with other flight control surfaces to function as speed brakes, vice the legacy that just had the big barn door between the tail.....or I should say little barn door, compared to its big MacAir brother.

[35_aoa]

And how do they operate when conformals are in place?

I could be mistaken, but my *guess* is that they are located forward of the fronts of the conformals.......if that isn't the case, then I'd imagine the FCS software would simply disable them. Talking out of my butt here, but those are the two reasonably possible solutions I can think of.

[spazsinbad]

Thanks all. OK Spoilers. As youse can see I know bugga all about the Shornets.

From Super Hornet NATOPS: https://info.publicintelligence.net/F18-EF-000.pdf (19Mb)

"The aircraft features a variable camber mid-wing with leading edge extensions (LEX) mounted on each side of the fuselage. Twin vertical tails are angled outboard 20 degrees from the vertical.

The aircraft is designed with relaxed static stability to increase maneuverability and to reduce approach and landing speed. The aircraft is controlled by a digital fly-by-wire Flight Control System through hydraulically actuated flight control surfaces: ailerons, twin rudders, leading edge flaps, trailing edge flaps, LEX spoilers, and differential stabilators. The leading edge of the wing incorporates a “snag,” which increases outboard wing area and increases roll authority in the approach and landing configuration. A speed brake function is provided by differential deflection of the primary flight control surfaces....

...2.10.1 Flight Control Surfaces. The aircraft has 12 primary flight control surfaces including leading edge flaps (LEFs), trailing edge flaps (TEFs), ailerons, twin rudders, horizontal stabilators, and spoilers. LEFs, TEFs, ailerons, and stabilators can be moved both symmetrically or differentially for pitch and roll control....

...2.10.1.1 Spoilers. The spoilers are mounted on top of the fuselage near the aft end of the LEX. The spoilers are controlled by the FCCs and have two fixed positions: 0° (down) or 60° TEU. The 60° TEU position is activated by the speedbrake function or when more than 15° TED stabilator is commanded (forward stick) above 22° AOA to aid in recovery from high AOA."
&
[Formation Take Offs] "...When Before Takeoff checks are completed and the flight is in position, each pilot looks over the next aircraft to ensure the speed brake is retracted (spoilers down), the flaps are set for takeoff, all panels are closed, no fluids are leaking, safety pins are removed, rudders are toed-in, nosewheel is straight, and the launch bar is up...."
&
"...Aircraft Differences (LOTs 21 - 22 Aircraft)
B.2.10.1.1 Spoilers. The spoilers are mounted on top of the fuselage near the aft end of the LEX. The spoilers are controlled by the FCCs and have three fixed positions: 0° (down), 13° TEU, or 60° TEU. The spoilers are commanded to the 13° TEU position at greater than Mach 1.5 to open engine inlet bleed air doors. The 60° TEU position is activated by the speed brake function or when more than 15° TED stabilator is commanded (forward stick) above 22° AOA to aid in recovery from high AOA...."

Then lots of text about how spoilers and other things work as speedbrakes under different conditions and control laws.

[quicksilver]

Thx. Spoilers they are. However, I note a couple things...

The description that spaz posted above states that the spoilers are near the aft end of the LEX. The picture from the article suggests that the conformals extend well forward of the ‘aft end of the LEX.’

Perhaps there Is an accommodation in the flight control laws for jets so-configured.

[35_aoa]

Thx. Spoilers they are. However, I note a couple things...

The description that spaz posted above states that the spoilers are near the aft end of the LEX. The picture from the article suggests that the conformals extend well forward of the ‘aft end of the LEX.’

Perhaps there Is an accommodation in the flight control laws for jets so-configured.

Yeah, I haven't seen a good picture for a while of the conformals from the side, but if they go forward far enough to interfere as you say, I'd imagine there would just be a mod to the FCS software to account. I would think it shouldn't be too hard to compensate with the other control surfaces. We already have PLM capability in approach configuration, which drastically alters the lifties using those very same control surfaces (and not the spoilers). It would seem that could be done in the traditional CAS with flaps/auto mode of the FCS by changing the gains/allowable movement. I'm no aero engineer though

[johnwill]

"...Aircraft Differences (LOTs 21 - 22 Aircraft)
B.2.10.1.1 Spoilers. The spoilers are mounted on top of the fuselage near the aft end of the LEX. The spoilers are controlled by the FCCs and have three fixed positions: 0° (down), 13° TEU, or 60° TEU. The spoilers are commanded to the 13° TEU position at greater than Mach 1.5 to open engine inlet bleed air doors. The 60° TEU position is activated by the speed brake function or when more than 15° TED stabilator is commanded (forward stick) above 22° AOA to aid in recovery from high AOA...."

The conformals appear to have vents cut into their top surfaces near the center to allow engine inlet bleed air escape above 1.50 M. But the spoilers are opened 13 deg TEU to allow the bleed air to exit the inlet. So the spoilers should open 13 deg with or without conformals installed. Thus the conformals would need a cavity on their lower surfaces to allow the spoiler to open, but only to 13 deg, and the spoilers lose their speedbrake function of 60 deg TEU with conformals loaded.

It seems FCS changes would be needed to limit the speedbrake to 13 deg with conformals and possibly to reprogram aileron, flap, stabilator, and rudder deflections during speedbrake actuation to maintain correct pitch balance due to presence of conformals and loss of spoiler speedbrake function.

[f119doctor]

"...Aircraft Differences (LOTs 21 - 22 Aircraft)
B.2.10.1.1 Spoilers. The spoilers are mounted on top of the fuselage near the aft end of the LEX. The spoilers are controlled by the FCCs and have three fixed positions: 0° (down), 13° TEU, or 60° TEU. The spoilers are commanded to the 13° TEU position at greater than Mach 1.5 to open engine inlet bleed air doors. The 60° TEU position is activated by the speed brake function or when more than 15° TED stabilator is commanded (forward stick) above 22° AOA to aid in recovery from high AOA...."

The conformals appear to have vents cut into their top surfaces near the center to allow engine inlet bleed air escape above 1.50 M. But the spoilers are opened 13 deg TEU to allow the bleed air to exit the inlet. So the spoilers should open 13 deg with or without conformals installed. Thus the conformals would need a cavity on their lower surfaces to allow the spoiler to open, but only to 13 deg, and the spoilers lose their speedbrake function of 60 deg TEU with conformals loaded.

It seems FCS changes would be needed to limit the speedbrake to 13 deg with conformals and possibly to reprogram aileron, flap, stabilator, and rudder deflections during speedbrake actuation to maintain correct pitch balance due to presence of conformals and loss of spoiler speedbrake function.

I find it quite interesting that the 13 degree position was added to increase inlet bleed flow above 1.5 Mn. That appears to be a pretty major change to the inlet function and how it matches to the F414 airflow characteristics. It would be interesting to know if there were any other inlet design changes in these lots of aircraft that made this change necessary, or if they discovered that increasing the bleed flow above 1.5 Mn improved the pressure recovery / engine thrust enough to offset the drag of the spoilers extended 13 degrees.

Or was there a boundary layer distortion getting to the engine face sufficient to cause an engine operability problem at these flight conditions. No mention of any retrofit of this spoiler inlet bleed capability to earlier blocks of the SH.

[aussiebloke]

Spaz’s NATOPS Flight Manual was written in 2008.
The section pertaining to spoilers on Lots 21-22 Aircraft Is referring to LRIP 1 and LRIP 2 production aircraft (I.e. the first Block I production Super Hornets) delivered in 1999/2000.

The information regarding 13 degrees TEU only applies to these two initial Lots. Subsequent Lots had spoilers with only two fixed positions: 0 degrees (down) and 60 degrees TEU. This can be seen in section 2.10.1.1 that spaz quotes.

[f119doctor]

Spaz’s NATOPS Flight Manual was written in 2008.
The section pertaining to spoilers on Lots 21-22 Aircraft Is referring to LRIP 1 and LRIP 2 production aircraft (I.e. the first Block I production Super Hornets) delivered in 1999/2000.

The information regarding 13 degrees TEU only applies to these two initial Lots. Subsequent Lots had spoilers with only two fixed positions: 0 degrees (down) and 60 degrees TEU. This can be seen in section 2.10.1.1 that spaz quotes.

Shows my ignorance regarding the Super Hornet. I was interpreting Lots 21-22 as later production lots, and not LRIP initial production. Did they keep the Lot numbers going forward from the Legacy Hornets, just to keep up the charade that the SH was just a minor development of the original?

Anyway, makes more sense that the 13 degree spoiler setting was eliminated as not needed after Flight Test was completed, vs adding it later as a new requirement.

[35_aoa]

Did they keep the Lot numbers going forward from the Legacy Hornets

Yes. Jets coming off the line now are lot 40+

[quicksilver]

“The conformals appear to have vents cut into their top surfaces near the center to allow engine inlet bleed air escape above 1.50 M.“ — JW

Now that you mention it, I seem to recall that feature as well, though I never knew their specific function.

Which brings me to my next observation and question —

Not unlike F-16, if the latest pictures we see above are accurate, the physical dimensions (and consequential aerodynamics and loads/structures) of the SH conformals have changed significantly since flown several years ago as a “demonstration” of the idea. The apparent production version does not appear to accommodate such vents, although I acknowledge they may simply be closed in the configuration we see above. Haven’t heard a peep of reporting on this apparent change from our intrepid stable of 21st century aerospace and defense reporters.

Anyone have any insight?

[marauder2048]

The apparent production version does not appear to accommodate such vents,

Are there recent photos of the production version?

[quicksilver]

Good question.

Here’s another — why is a BA ‘artists rendition’ of the conformals in a July 2020 article at odds w the demonstration configuration flown several years ago?

There are potentially lotsa good reasons, but it’s still worth wondering, along with flight test progress of any/either configuration.

[johnwill]

Here is the source of my comment on conformal tank vents.

[quicksilver]

Thx.

This is the photo that captured my eye. ‘Appears’ to be more refined aerodynamically.