1965 VT-17A McDonnell V/STOL Transport Study

[Mark Nankivil]

Hi All -

A retired McDonnell Douglas engineer passed along a package of drawings to the Museum yesterday and the attached drawing was one of them. Tiny wings!

Enjoy the Day! Mark

 

[Orionblamblam]

Tiny wings!

The idea is that with a VTOL system, you only need enough wing for efficient horizontal cruise, which means much less wing than is needed for runway takeoff. This greatly lowers weight and drag. Of course if something goes wrong the glideslope is a little harsh.

 

[hesham]

Great find my dear Mark.

 

[JohnR]

Tiny wings!

The idea is that with a VTOL system, you only need enough wing for efficient horizontal cruise, which means much less wing than is needed for runway takeoff. This greatly lowers weight and drag. Of course if something goes wrong the glideslope is a little harsh.

Off topic, but you have answered a question I was posing to myself. Why did the P1154 have such small wings?

Thank you.

Regards

 

[Orionblamblam]

Off topic, but you have answered a question I was posing to myself. Why did the P1154 have such small wings?

Thank you.

It's a universal tradeoff. Even with CTOL aircraft, sometimes the designers put tiny little wings on the plane (see: F-104). It makes takeoff and landing sporty, but it makes high speed flight much easier and more fuel efficient.

I could see a military transport like this one, with tiny little wings optimized for cruise, but I can't readily imagine the FAA being too happy about a civilian jetliner with no ability to safely glide to a landing.

 

[Stargazer]

I could see a military transport like this one, with tiny little wings optimized for cruise, but I can't readily imagine the FAA being too happy about a civilian jetliner with no ability to safely glide to a landing.

I thought no airliner since the 747 was able to "safely glide to a landing" anyway, being all aerodynamically unstable and kept in the air only because of constant computer-controlled change of incidence of the flaps, ailerons, etc. Isn't that so?

 

[Mike Pryce]

Many are FBW, but the APU/batteries power the control systems if the engines go.

 

[TomS]

I could see a military transport like this one, with tiny little wings optimized for cruise, but I can't readily imagine the FAA being too happy about a civilian jetliner with no ability to safely glide to a landing.

I thought no airliner since the 747 was able to "safely glide to a landing" anyway, being all aerodynamically unstable and kept in the air only because of constant computer-controlled change of incidence of the flaps, ailerons, etc. Isn't that so?

Fly-by-wire is not the same as having relaxed stability. Airliners with FBW can generally fly OK without the computers, as long as there is still power to the FBW system itself. Even Airbuses can go to Direct Law when the computers fail. In Direct Law, the flight controls directly control the positions of the control surfaces.

As for post-747 airliners not being able to glide safely, I give you the Gimli Glider, a Boeing 767 that glided something more than 20 miles with no power except the Ram Air Turbine to power the control surface hydraulics and batteries for the backup flight instruments.

 

[Stargazer]

Many are FBW, but the APU/batteries power the control systems if the engines go.

Fly-by-wire is not the same as having relaxed stability. Airliners with FBW can generally fly OK without the computers, as long as there is still power to the FBW system itself. Even Airbuses can go to Direct Law when the comuters fail. In Direct Law, the flight controls directly control the posiitons of the control surfaces.

Point well taken. A loss of engine power wouldn't mean a loss of controls.

Which makes me think that a neatly directed electro magnetic pulse wave to kill off onboard computers and electronics would be the most effective weapon of all against modern aircraft. Wonder how far this technology has gone and why it's not already in use.

 

[XB-70]

McDonnell's submission to the CX-6 competition?
The programm was canceled in 1967, so it would fit in the timeframe.

 

[AeroFranz]

I could see a military transport like this one, with tiny little wings optimized for cruise, but I can't readily imagine the FAA being too happy about a civilian jetliner with no ability to safely glide to a landing.

I thought no airliner since the 747 was able to "safely glide to a landing" anyway, being all aerodynamically unstable and kept in the air only because of constant computer-controlled change of incidence of the flaps, ailerons, etc. Isn't that so?

A modern airliner might have a cruise L/D ratio of 21. Windmilling fans might cut that down a little bit, but not much - say 18? So you can probably get a glide ratio of one foot lost every eighteen, or a little over three degrees glide slope.

 

[hesham]

McDonnell's submission to the CX-6 competition?
The programm was canceled in 1967, so it would fit in the timeframe.

Hi XB-70,


I think you are right,and McDonnell submitted a proposal for this contest;


http://www.secretprojects.co.uk/forum/index.php/topic,1008.15.html

 

[GTX]

Fly-by-wire is not the same as having relaxed stability. Airliners with FBW can generally fly OK without the computers, as long as there is still power to the FBW system itself. Even Airbuses can go to Direct Law when the computers fail. In Direct Law, the flight controls directly control the positions of the control surfaces.

As for post-747 airliners not being able to glide safely, I give you the Gimli Glider, a Boeing 767 that glided something more than 20 miles with no power except the Ram Air Turbine to power the control surface hydraulics and batteries for the backup flight instruments.

Indeed. I would also point to Air Transat Flight 236 which involved an Airbus A330 that suffered a complete power loss.