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Sundowner

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About Sundowner

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  1. I've got some official numbers for AEI situations... it is a bit better than I expected. Earlier I estimated glide ratio at 3:1 in a glide, apparently it is closer to 4.5:1 - slightly better than Space Shuttle, unfortunately speeds have to be maintained pretty high - depending on weight - from 140 to 200 kts, and 120-150 at touchdown. With 3500fpm descent, that might be quite a ride... The AEI in hover topic is apparently avoided, with everybody having fingers crossed that an re-light of engines will occur before the impact. Anyway pilots are told to bring the bird down at 110kts, and attempt run-on landing at 60kts... now, you can do the math how high you have to be in a hover to do this.
  2. I'm looking for help with a trivial personal project I'm currently on, and I need someone who know the machine, and can help me with few things. If you work with one, please, drop me a PM, and I'll respond with what I'm looking for exactly. Thanks.
  3. Another change of topic.... Can anyone shed some light on the logic behind the "metallic" paint on those MV-22s ? Last time a metallic paint was used, it was on F-20 Tigershark - it was called "BMW gray" and made its FCR inoperable, what's up with it on Osprey ?
  4. Actually you would be right... if it was an Russian helicopter
  5. Well at least we agree at that one Now seriously, why do anyone want ant tiltrotor C-130 ? Seriously, CH-53K or Mi-26 will do the job better and it will cost less money if you're really need an vertical tekeoff/landing. An C-130J will do the job better and also with less money if you're just about the speed. If you need to put something in confined area, just use Helicopter, or drop it on APADS-like system from regular transport plane. If you need to take something heavy from confined area, well use the helicopter, that BTW was designed to do many other tasks, not bought only to wait for someone to putt a 20 ton equipment on a football field size pad. I do see need for the Osprey and BA-609, you know, fast Marines insertion/extraction, and short-mid range fast CSAR runs etc. But why would anyone need an vertical takeoff/landing Hercules is beyond me.
  6. Do I understand you right ? The rescue chute for the Osprey passengers would have to meet the same standards as, lets say T-10D ? If so it may be a problem... the Russian S-4 parachute I'm referring to all the time is a derivate form parachute used in KM-1 Ejection Seat of MiG-21 - that was the first Soviet zero-zero ejection seat. It is designed totally different from the paratrooper chute, what the rigger told me it have very little steering authority, but by itself steers into the wind and have rather low descent rate compared to the combat chutes.
  7. Exactly, the use of parachutes in helicopters is a bit iffy, in most emergences, you can still land safely. The only few that are catastrophic are the loss of the main rotor, total failure of the main gearbox, and uncontrollable fire. Parachutes on helicopters can be used as long as the glide ratio is no less than 1:1 (1:2 is somewhat standard in autorotations), and you can't achieve that without lift, so in helicopters, the only time parachutes would be practical is in case of a fire on board. The thing is - only cases I'm aware off that kind of fire were during take-offs, or at low altitude due to enemy fire (mostly CH-46 thing), so parachutes would not be practical. Although most of the Russian helicopters have them stored in the crew seats, for 27 years use of Mil Mi-14s here, there were not even one event requiring to use them, even though 4 helicopters were lost due to accidents (failed water landing at night, multiple bird strike, and one that hit trees... plus there was one that had to ditch, but there were no injuries) non of them allowed the use of parachutes, ass most accidents were on very low level and give crew no chance to react. Parachute in helicopter is a ballast... Tilt rotor is a different animal. Even if the 'tilt can glide in case of both engine out scenario, than the contact with the ground will be at very high speed, and will be dangerous. Bailing out in that case may be an option. So let me comment on your first post: That's true, even with an emergency chute, training is needed, but when having in mind hitting mother earth in an aluminum-titanium, fuel filled box at 150+ kts... I think having only broken legs may be something even untrained people would consider a lower risk I don't have data for US/UK made emergency chutes (like those in ejection seats), but the Russian made S-4 is rather heavy for its type and weight 33lb, with 20 on board that's 660lb... UK/US made ones should be half of that. And yes every parachute have to be regularly unpacked, checked, dried, and packed... but not all at once ! That would need like what? 1 person per 10 Ospreys to do ? In here there is 13 Mi-14s, thats 58 parachutes on aircrafts, twice more in storage... and that's maintained by 3 people, that are also responsible for ALL other survival and personal flight equipment (helmets, life rafts, life jackets, immersion suits, etc.) and they are not overworked at all! I would say 0.3 second is needed to emergency open an ramp... just blow the hinges, let it fly away Well in that case an emergency egress should be practiced on the mock ups as a standard "boot camp" training, this can be done and won't cost much. The CG change will be only in one axis, I think the crew can menage that, as they are already superhuman at that time - high on adrenaline That's non-issue. The chute can be attached from the get-go. The chutes are in the seats, the seats are rarely removed, so the line from the chute to the sealing one can be attached when the chute is being mounted in the seat. it will only require something to hide the line so it wont be snagged during normal procedures - some sort of velcro'ed patch will suffice. As long as the glide ratio is better than 1:1 than it's also a non-issue... when worse, well let the crash worthy seats work their magic. Yes, that's why parachute can't be the only safety device - quite different than Russian engineers think Parachute is only a part of the survival system, used when above certain altitude, airspeed and attitude. This may sound strange, but I don't remember any S-4s failures and also any failures of the chutes in modern ejection seats. Those are very reliable and very safe chutes, designed to put man safely on ground, even if he's unconscious! Don't try to compare the emergency chutes that we're talking about with typical paratroopers or civy free fall chute's - those were designed for totally different roles.
  8. Strapping the chute on - is not a problem, as its harness IS the seat harness, you would just have to disconnect it from the seat "shell", than hook up, and make the way to the ramp and jump. And yes the landing part may be a bit of a problem The Russian S-4s are quite safe even for untrained individuals though, accidents will happen only if the person will try to "help" the chute I just wonder what's the V-22 Flight Manual say for both engines out scenario, both in forward flight, and in hover. That would clear a lot.
  9. I don't see the one engine out scenario a problem in tilt rotors, as they usually have enough power to get out of the situation safely. I'm only concerned about the dual-engine-out scenario. And yes, I have some experience with parachutes, mostly S-4 rescue parachute that are a part of Mi-8/14/17 seats - they weight 33lb (life raft included), those are rather old technology, I think Martin-Baker could design similar system in half (or less) the weight.
  10. If I remember correctly the Bell 206 have a glide ratio of 2:1 , the same as "dirty" F-104 (flaps, gears - all out) the difference is, an auto rotating Helicopter, can stop, than land... an "gliding" F-104 would hit the ground at 250kts, than try to stop. Space Schuttle is not much better with 4:1 just before touchdown. I'm no Aviation Engineer, but to my understanding, glide ratio is lift divided by drag... helicopters are very draggy, so is the osprey - it uses the same power of C-23J Spartan cargo aircraft, to achieve 4/5th of its speed. The lift is: coefficient x half-density, x velocity squared, x lift area. The wing area of Osprey is 3 times smaller than that of Spartan, thus giving it 3 times less lift. So V-22, with higher drag and lower lift considered, should have the glide ratio nearly 4 times worse than the C-23J at the same velocity. The earlier Alenia G.222 which was a little less draggy then the new Spartan had an glide ratio of 12:1... that would put V-22 at 3:1, little more than helicopters and F-104, but less than Space Shuttle... mind you both "fixes" need to perform touch down at speeds that are maximum for V-22 powered flight. I don't see how "gliding" would work with Osprey. Both engines out will be catastrophic in that bird, no matter when or where. I'm not biasing the tiltrotor design, I see it strengths as you posted, when you need transport something fast into tight spot. But the safety is worse than both helicopters and fixed wing. Both engines out scenario have higher probability than drive shaft failure on tandems. For drive shaft failure, you need an purely physical damage or material over-stress to occur. Engine may go out because of those causes + few others, like low fuel/oil quality, salt buildup on the intakes, not enough oxygen in the air (water/dust ingestion) etc. Tilts need more survival systems, like ejection seats, crash worthy troops seats with stored parachutes, or/and impact cushion systems (Israelis are developing exterior airbags for helicopters). From survival stand point, tilts are not yet ready for service.
  11. Right now we're discussing an VTOL aircraft, and the chances crew have with both engines out. Comparing to Space Shuttle is not really good. Yes, the space shuttle have even higher wing loading (420lb/ft^2), but space shuttle isn't really "gliding", its actually falling down at 10'000 feet per minute, only because of its speed at reentry its flight path is not very steep - than just before touching down it is rotated to very high AoA - near stall - when that small wing generates the biggest amount of lift, and that's done at 424mph, it just slows down the beast, and cushion the landing which is made with still with 215 mph. F-104 can't do that, the Osprey can't do it either, mainly because of its speed, and elevators authority. When you're cruising at 200kts and both engines out, your options are very limited. And this may... and will happen in random places, speeds and altitudes, not one that hundred of people and computers calculated before your take-off. Osprey can't glide, and can't autorotate (here we come with also huge disc load), if both engines go out, it better be on the ground, cause every hight and attitude may be lethal.
  12. I'm not sure that anything that have wing load of 110lb/ft^2 empty(!) can glide... F-104 couldn't, and it had only 71lb/ft^2
  13. The VTDP/X-49 is an interesting project, but have one major drawback. To achieve speeds similar to tilts and X2, it requires wings... and history proved it's not really a good idea to put them on helicopters, as they limit hover capabilities, and cause problems when flying backwards - that's why they were detachable on Mi-6, and why Mi-24 drivers look with envy at the Blackhawk jocks . Yes, the B360 was an interesting project, somewhat a "SpeedKnight" although I wouldn't wait for Boeing to show something like that in near future. Not when the V-22 is made by them. The Osprey is their new B360.
  14. To my understanding, tandem, like on Piasecki birds is for large transport helicopters only, because the rotors dimensions dictate overall fuselage size. For example, making an helicopter with two Bell 407 rotors would end up in a machine size of S-92... that couldn't really carry much load for its size. The B234 is probably somewhere the optimal size for that system. There is also problem of money. Two big gearboxes, and two big rotors with full sized blades is definitely more expensive than one big gearbox with rotor + some small gearboxes and small rotor/fan.
  15. The 30ft is my estimation, not calculated number. The biggest issue with ABC systems is the rigidness of the blades, as it have to be much higher than normal blade. And the longer we go, the forces on that blade grow exponentially. 30ft blade compared to 15ft one, will have to be 4 times stronger... or even more. And there we hit the wall which are the known materials, and design limitations.
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