75 votes
Accepted

What is the purpose of the extra wheel on the XB-70 main gear?

It is a sensing wheel that is part of the antiskid braking system. It contains an electronic sensor to measure the true groundspeed of the airplane. See NASA Technical Note D-4836, Landing Loads and ...
Fred Larson's user avatar
  • 2,468
48 votes
Accepted

Why Didn't the USSR Build An X-15?

I like the X-15, it was certainly an amazing airplane, but the truth is there were few benefits to the space program from the X-15. It was far from a critical or necessary step: The Mercury space ...
GdD's user avatar
  • 53.7k
47 votes

What is this red canister on the tail of the YF-22?

The canister contains a small parachute and either a spring or an explosive charge to kick the chute out when it is needed. It is a precaution for spin flight tests, that's why it is called a spin ...
Peter Kämpf's user avatar
39 votes

What is this 3-engine beast?

Vickers Viscount C-FTID-X Pratt & Whitney Canada's PT6 test bed with a PW100 mounted on the nose. 01/22/2007. Remarks by Jack McKillop: "This aircraft made its first flight on February 25, ...
Mike Sowsun's user avatar
  • 37.7k
38 votes
Accepted

What is this odd aircraft?

It appears to be a Celera 500L, owned by Otto Aviation Group. This article has more information: "Unmasking The Bullet-Shaped Mystery Aircraft After It Reemerges At Victorville" The registration ...
John Wiseman's user avatar
  • 1,709
30 votes
Accepted

What is this red canister on the tail of the YF-22?

It is a spin recovery/stabilization chute, installed during testing for high AoA test flights. The following image shows it being deployed on the ground. Image from fas.org
aeroalias's user avatar
  • 100k
29 votes

Why Didn't the USSR Build An X-15?

I'll complement GdD's answer from a slightly different perspective. In the history of aerospace engineering... Wait, there is a problem right there. Due to various historical reasons, there was ...
Zeus's user avatar
  • 9,053
26 votes
Accepted

Why did the AvroCar fail to fly above 3 feet?

From what can be gleaned from the Net, it was instability. The Avrocar had plenty of power but was unstable. The resulting behavior made it uncontrollable when leaving ground effect. In this ...
Peter Kämpf's user avatar
25 votes
Accepted

What is the 'arm' at the rear of the X-29?

Two X-29's were built, and the only difference between the two is that #2 has an externally mounted spin recovery chute attached to the tail. That is what you are seeing in this picture. The chute is ...
Ron Beyer's user avatar
  • 36.2k
25 votes

Why was the skid landing gear located so far aft on the X-15?

Indeed as Peter Kämpf said, the skids were only used for landing; the takeoff on X-15 was done by attaching it to the starboard wing of a modified B-52, known as the NB-52A. This was the only way it ...
Aditya Sharma's user avatar
21 votes

What is this odd aircraft?

$\sf \color {SteelBlue} {\text {Known facts}}$ Seen at Southern California Logistics Airport (Victoville, KVCV) Parked at transient parking On April 12th, 2017 $\sf \color {SteelBlue} {\text {...
19 votes
Accepted

How can the Perlan II glider climb to 90,000 feet?

Perlan II will climb to extreme altitudes on wave lift, not thermal lift. Wave lift is created when strong winds blow approximately perpendicular to a mountain range, and the wind speed increases ...
Ben H's user avatar
  • 929
18 votes
Accepted

What was enabling control to the pilot on the Snecma C-450 Coléoptère?

Great find, a vehicle with so many new design features in a time before Computed Fluid Dynamics, and hard to test in a wind tunnel where the device could only be mounted in a fixed position. From ...
Koyovis's user avatar
  • 61.6k
17 votes
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Why was the skid landing gear located so far aft on the X-15?

The X-15 landing speed was around 200 mph. The primary reason to have the skids so far back would be directional stability, which would be helped greatly by a trailing parachute. The placement of the ...
Robert DiGiovanni's user avatar
15 votes
Accepted

Could flywheel type gyros stablize a plane?

I actually have a lot of experience in the shipboard systems that you are talking about. First, the gyro's do not keep the boat upright, they counter the rolling effect of waves but they cannot ...
Ron Beyer's user avatar
  • 36.2k
15 votes
Accepted

What is this Lockheed Martin plane?

Lockheed Martin Sabre Warrior UCAV (concept): Source Source From Defence Forum India: The Sabre Warrior drone is 46 feet long, with a 36-foot wingspan, capable of taking off with 30,000 pounds ...
mins's user avatar
  • 71.8k
15 votes
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What kind of Chinook helicopter/airplane hybrid is this?

It‘s a BV-347 technology demonstrator: In 1969, the Army and then-Boeing Vertol entered into a partnership to improve upon their cargo helicopter fleet, and thus the BV-347 was borne from a CH-47A ...
Cpt Reynolds's user avatar
  • 4,797
15 votes
Accepted

Are ex military airplanes experimental?

"Experimental" refers to a particular category of airworthiness certification available for an aircraft. 14 CFR §91.203 requires all "civil aircraft" to have an airworthiness ...
TypeIA's user avatar
  • 14.2k
13 votes

Why did the YF-23 never enter service?

The decision was non-technical You can hear it from the test pilots themselves: The rating was actually based on stop lights. Individual requirements (e.g. ...
Krishty's user avatar
  • 231
13 votes

Has anyone researched or built an aircraft that controls pitch and roll by pumping liquid within the airframe?

The aerodynamic forces resulting from surface deflections are orders of magnitude larger and faster (in their rate of change) than the gravitational forces obtainable by shifting the centre of mass. ...
AEhere supports Monica's user avatar
12 votes

Why do forward-swept winged fighters have the main wings in the back?

These are just two canards with forward-swept wings. There is no general rule that the wing has to be in the back once it is swept forward. In both particular cases the configuration was selected to ...
Peter Kämpf's user avatar
12 votes

Why was the Sukhoi Su-47 Berkut never adopted for service?

I do not have inside knowledge, but think it is easy to explain why the Su-47 did not progress beyond the prototype stage: Sukhoi enjoyed great export success with the Su-27 and its derivatives in ...
Peter Kämpf's user avatar
11 votes
Accepted

How does the X-59 achieve low-noise supersonic flight?

As of the date of this answer, the X-59 has not yet flown, but according to the designers... The ground noise is expected to be around 60 dB(A), about 1/1000 as loud as current supersonic aircraft. ...
Juan Jimenez's user avatar
  • 12.8k
10 votes
Accepted

May I fly with passengers on a homebuilt experimental airplane with only a simple PPL?

Yes, you can, you don't need anything other than the words EXPERIMENTAL to be visible by the passenger. Your PPL is fine for flying experimentals, although like any ...
Ron Beyer's user avatar
  • 36.2k
10 votes

Why Didn't the USSR Build An X-15?

Great question, but no, the X-15 was not a "critical and necessary step on the path to manned space flight" at all, it was used to test the feasibility of sustained and controlled hypersonic flight ...
Robert DiGiovanni's user avatar
10 votes
Accepted

Are there any variable-diameter propellers?

The 1994 NASA report Wind tunnel test of a variable-diameter tiltrotor model documents wind tunnel tests of a 1/6th scale variable-diameter tiltrotor. Fig. 3 on p. 4 (p. 12 of the pdf) shows the ...
Camille Goudeseune's user avatar
9 votes
Accepted

Why was the experimental MiG 1.44 so similar to the experimental TKF-90?

I once led a group of Antonov engineers through the aircraft exhibition of the Deutsches Museum in Unterschleissheim near Munich. There are two halls connected by a walkway, and from that walkway you ...
Peter Kämpf's user avatar
9 votes
Accepted

Has anyone researched or built an aircraft that controls pitch and roll by pumping liquid within the airframe?

So far, only pitch. Fuel is pumped between tanks to trim the aircraft. This is especially helpful for supersonic aircraft, because their center of pressure moves by a quarter of the wing chord between ...
Peter Kämpf's user avatar
9 votes

Why do experimental aircraft have such long tubes on the nose?

Yes- you can see an array of little doodads sprouting from the pitot probe in this photo, they are for accurately measuring the direction of airflow in 3 dimensions. They also are long to ensure that ...
niels nielsen's user avatar

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