Debates
27 Dec 07
28 Dec 07
1 edit
Originally posted by Sam The Shamlol
In fairness to Thousand, he was inquiring about the possible advantages/disadvantages of the method for VTOL, that is the Osprey's wings actually shifting from helicopter type flight to airplane flight versus the downward porting of thrust in the Harrier. He wasn't implying the applications of the two aircraft could be compared.
I'm going to go n nothing but a gut instinct. Any VTOL fans out there that know what they're talking about?
Ok. Now I understand. I will give it a go in comparing them as you describe... I think.
Think of a really nice van that carries ten workers in a carpool at fifty miles per hour to work every day. It has lots of nice doors and a big ole slow rpm engine that ain't fancy but gets you there. It's exhaust comes out the back end and stinks things up. Think Osprey.
Think of a nice 911 Porsche on a race track with one guy in it having a go at 200 mph. It's exhaust comes out the back and stinks things up. Think Harrier.
Now to the part where we compare one type of air pointed toward the ground from a big old propeller to the OTHER type of air pointed toward the ground from a big old turbine. As near as I can tell, Newton’s law can't tell the difference between the two types of air.
The equal and opposite reaction from the propelled air on the Osprey which has a loaded weight of 21,500 kg gives it the apparent sex appeal of a St. Barnard dog. The equal and opposite reaction from the propelled air on a Harrier with a loaded weight of approx. 10,410 kg gives it the sex appeal of a greyhound dog.
Does this help?
28 Dec 07
Originally posted by Sam The ShamI probably should have put this in Pozers and Puzzles.
In fairness to Thousand, he was inquiring about the possible advantages/disadvantages of the method for VTOL, that is the Osprey's wings actually shifting from helicopter type flight to airplane flight versus the downward porting of thrust in the Harrier. He wasn't implying the applications of the two aircraft could be compared.
I'm going to go ...[text shortened]... n nothing but a gut instinct. Any VTOL fans out there that know what they're talking about?
28 Dec 07
Originally posted by Sam The Shamthe osprey used to crash a lot.
In fairness to Thousand, he was inquiring about the possible advantages/disadvantages of the method for VTOL, that is the Osprey's wings actually shifting from helicopter type flight to airplane flight versus the downward porting of thrust in the Harrier. He wasn't implying the applications of the two aircraft could be compared.
I'm going to go ...[text shortened]... n nothing but a gut instinct. Any VTOL fans out there that know what they're talking about?
28 Dec 07
Originally posted by StarValleyWyUmmmmmm OK. Now think of an Osprey fluttering around as a true helicopter for a few hours with it's wings up, which it can do. Now picture the Harrier running out of gas after 2 minutes showing off it's hover ability.
lol
Ok. Now I understand. I will give it a go in comparing them as you describe... I think.
Think of a really nice van that carries ten workers in a carpool at fifty miles per hour to work every day. It has lots of nice doors and a big ole slow rpm engine that ain't fancy but gets you there. It's exhaust comes out the back end and stinks things u ...[text shortened]... d weight of approx. 10,410 kg gives it the sex appeal of a greyhound dog.
Does this help?
29 Dec 07
Originally posted by spruce112358well, the osprey could swing its rear end around and engage the harrier in a dogfight ...
???
The Harrier is a fighter jet while the V22 Osprey is a troop transporter "armed with one 0.308 in (7.62 mm) machine gun pointing rearward that can be fired when the loading ramp is lowered."
29 Dec 07
Originally posted by zeeblebotYes. Think of a chihuahua against a tiger.
well, the osprey could swing its rear end around and engage the harrier in a dogfight ...
The osprey would be nothing but a few sad feathers.
Slower, not as maneuverable, not as capable to fight...
If I were to "put one against the other"... and If I were a military man, I would be fired. You don't send a delivery truck to war against a superior aircraft. Now if you want to deliver a covert action team into a hard to reach area... you use the osprey truck. It is fast... for a truck.
29 Dec 07
1 edit
Originally posted by Sam The ShamThe group I was in chose a VTOL design for an RFP (request for proposal) we had to submit as part of our final aircraft design course. Lets just say that after looking at every alternative after half a semester had passed we gave up on VTOL because of the weight and cost we would be adding to the design. The rfp was for an Air Taxi with range of 1000nm to carry 4 men with two crew and room for luggage and golf bags. We ended up with an STOL design as to be able to price a plane with a life cycle cost that would be attractive for a small commercial concern to run effectively scotched the idea for VTOL. Apart from the Bell/Augusta 609 which is a direct spin off of the V22 Osprey there are no actual running commercially viable VTOL designs to date.
I'm going to go out on a limb and guess that the Osprey is a lot easier to fly and transition between VTOL and regular flight, but I'm basing that on nothing but a gut instinct. Any VTOL fans out there that know what they're talking about?
The main reason for that is basic physics. A plane in flight can easily produce enough lift to overcome its weight requiring relatively little thrust to maintain a given altitude. Overcoming that weight directly with either vectored thrust or a tilt wing/tilt rotor design means that if you weigh 5000lbs at a minimum you need 5000 lbs of thrust to take off or land. This is where the problem starts and never quite goes away, because you always end up with having to design more plane than your initial requirement of crew/passengers and payload just so that you can have enough thrust at take off and landing.
While helicopters make it look easy and seem light enough, they have problems with range and reliability. All planes do to some extent, but helicopters more so. The secret of the Osprey is the size of the rotors. They are huge. But they can hover all day. The problem with them is the redundancy that has to be designed into them so that one of the two turbo prop motors has to be able to produce the required thrust for the critical take off landing phase should the other fail during this crucial stage. This requirement adds weight and mechanical complexity to the design, which adds potential for things to malfunction.
In terms of the transition from vertical to horizontal flight it doesn't look pretty. I haven't flown in one but I dont know that I would want to either. The thing is you have to gain altitude and then as your wings tilt down to the horizontal the plane goes into a very shallow dive from which normal flight is established. Its this giving up of potential for kinetic energy thats the dangerous thing in the design imho. They are not designed to take off and make a smooth transition. There will always be a heart in mouth moment where they will drop as much as a couple of hundred feet to get underway. However for what the Osprey can accomplish in its ability to drop in and out of inaccessible places, the risks are considered worth it.
Unfortunately if you work out the thrust required to accelerate the plane vertically from rest into a forward velocity profile such that wings can take over and produce the lift required to stay in flight, you work out the the solution they have with the Osprey is about as good as it gets.
29 Dec 07
Originally posted by kmax87why not use a catapult?
The group I was in chose a VTOL design for an RFP (request for proposal) we had to submit as part of our final aircraft design course. Lets just say that after looking at every alternative after half a semester had passed we gave up on VTOL because of the weight and cost we would be adding to the design. The rfp was for an Air Taxi with range of 1000nm to car ...[text shortened]... n flight, you work out the the solution they have with the Osprey is about as good as it gets.