Forum: General F-22A Raptor forum

The F-22 may have a fixed inlet, but has 'slots and slats' to divert airflow, where other 'traditional fighters' (not mentioned specifically on their 2 whole aircraft list) have 'moving parts'

The F-35 approach to dealing with this issue is truely remarkable in that it is not only simpler and cheaper to build, it also offers better performance over older designs

FYI, the boundary layer gap of the F-16 inlet is set at precisely 3.3 inches for optimal Mach 2 performance. And it does not matter if an inlet is moveable or fixed.

What is the reason the gap is designed for Mach 2 performance if the plane very rarely operates at that speed. Wouldn't it be designed for the speed at which it is normally operated at.

No doubt that DSI is much cheaper and simpler, but what kind of better performance does it offer? Lower overall drag of the airframe, some advantages in terms of pressure recovery ratio?

In particular, the present invention does not require a boundary layer diverter, a side or splitter plate, a boundary layer bleed system or an overboard bypass system. Furthermore, the present invention has no moving parts. This reduction in complexity reduces the tactical fighter aircraft's empty weight, production cost, and maintenance support requirements. These savings are estimated to be 250 pounds per aircraft, $225,000 per aircraft, and 0.03 maintenance man hours per flight hour, respectively.

Flow Field and Performance Analysis of an Integrated Diverterless Supersonic Inlet. In this paper the computed flow and performance characteristics at low angle-of-attack (AOA) of an integrated Diverterless Supersonic Inlet (DSI) are presented near its design mass flow rate. The subsonic characteristics are evaluated at M?=0.8 while the supersonic characteristics are evaluated at M?=1.7, which is near the design Mach number for the intake. In addition to the external flow features, the internal intake duct flow behavior is also evaluated. The results of this study indicate effective boundary layer diversion due to the “bump” compression surface in both subsonic and supersonic regimes. At M?=1.7, the shockwave structure (oblique / normal shockwave) on the “bump” compression surface and intake inlet is satisfactory at intake design mass flow ratio. The intake duct flow behavior at subsonic and supersonic conditions is generally consistent with “Y” shaped intake duct of the present configuration. The secondary flow structure inside the duct has been effectively captured by present computations. The computed intake total pressure recovery at M?=1.7 exhibits higher-then-conventional behavior at low mass flow ratios, which is attributed to inlet design feature. Overall computed subsonic and supersonic total pressure recovery characteristics are satisfactory under the evaluated conditions and are also in agreement with wind tunnel test data.

The F-35 approach to dealing with this issue is truely remarkable in that it is not only simpler and cheaper to build, it also offers better performance over older designs. Hope this helps answer your question!!

TEG, back to tech. I spent years selling centrifugal compressed air tech and always had to concern myself with choke and surge during review. How does DSI deal with surge (or lack of air) because the intake cannot physically open?