Northrop X-21 Laminar Flow Control

[blackkite]

Hi!

https://www.airforcemag.com/PDF/MagazineArchive/Documents/1963/0863control.pdf
http://nhungdoicanh.blogspot.com/2010/07/northrop-x-21.html
https://kerbalx.com/NorthAmericanAviation/Northrop-X-21

 

[blackkite]

Hi! Two stage turbine drive compressor air suction system. (New Scientist, 1st of Nobember 1962, from page 250)
Low pressure compressor was driven by engine bleed air turbine and high pressure compressor was driven by engine bleed air burned turbine.
https://books.google.co.jp/books?id=aEjiMdgfJJkC&pg=PA252&lpg=PA252&dq=Northrop+LFC+Supersonic+Transport+study&source=bl&ots=xdc0EIYNb-&sig=ACfU3U2AL9nFu4YkMTm9fEiD0M7GJoOmMw&hl=ja&sa=X&ved=2ahUKEwigltLCkL3oAhVHM94KHe2HCNsQ6AEwAHoECAgQAQ#v=onepage&q=Northrop LFC Supersonic Transport study&f=false

 

[blackkite]

Northrop : An Aeronautical History, Fred Anderson
https://books.google.co.jp/books?id=-YEEDgAAQBAJ&pg=PA196&lpg=PA196&dq=NORTHROP+X-21+BLEED+BURN+TURBINE&source=bl&ots=t75X5FO5va&sig=ACfU3U1DBNcgkQKxEgZaPKTkPZyr6ECKyg&hl=ja&sa=X&ved=2ahUKEwjahobRor_oAhXNc3AKHc4fANYQ6AEwAXoECAkQAQ#v=onepage&q=NORTHROP X-21 BLEED BURN TURBINE&f=false

 

[Viper2000]

The X-21 is featured in the section on Laminar Flow starting on page 123 of this NASA monograph.

 

[blackkite]

Hi! This LFC system is hard.
"Practical application of the concept proved unworkable, since rain, dirt, dust and other particulates clogged the slots."
https://www.globalsecurity.org/military/systems/aircraft/x-21.htm

 

[blackkite]

Hi! Overview of laminar flow control, NASA.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19980232017.pdf

 

[hesham]

From Air Force magazine 1961,

what was this Project for Northrop Laminar Flow Control ?,or just a hypothetical
design ?.

 

[Whisperstream]

From Air Force magazine 1961,

what was this Project for Northrop Laminar Flow Control ?,or just a hypothetical
design ?.

The system was tested in 1963 on the X-21A. Northrop modified two WB-66Ds (AFSN 55-0408 and 55-0410) as test vehicles for laminar flow control (LFC) systems. The aircraft was fitted with a completely new wing of increased span and area, with a sweep reduced from 35 degrees to 30 degrees. The wing has a series of span-wise slots through which turbulent boundary-layer was sucked away, resulting in a smoother laminar flow operation, resulting in reduced drag, better fuel economy, and longer range. The underwing podded J71 engines were removed and replaced by a pair of 9490 lb.s.t General Electric XJ79-GE-13 turbojets mounted in pods attached to the rear of the fuselage sides. Bleed air from the J79 engines was fed into a pair of underwing fairings, each of which housed a bleed-burn turbine which sucked the boundary layer air out through the wing slots.

Testing proved that the overall concept was feasible, and a substantially improved range was obtained. However, it was found essential to keep the tiny wing slots spotlessly clean for effective operation, and this and other maintenance difficulties made the concept too costly for practical applications.

The last time I saw these airframes they were sitting derelict on the Photo Resolution Range portion of the Precision Impact Range Area at Edwards AFB. There was some talk of restoring one for the Air Force Flight Test Museum but I don't know whatever came of that.

 

[Grey Havoc]

With current technology, those maintenance problems might well be solvable now. Indeed, it probably would have probably been the case by the 1980s. Which makes me wonder, where there any attempts to resurrect this technology at that time?

 

[flateric]

View: https://www.youtube.com/watch?v=8v2HtiuaALc

 

[hesham]

From, United States Aircraft Missiles and Spac 1962.

 

[fightingirish]

The Northrop X-21A took its first flight on April 18, 1963.

https://flic.kr/p/2rjg2EH

View: https://flic.kr/p/2rjg2EH
Source:
https://www.britishpathe.com/asset/247057/