What Steve said; I'd also like to point out that countries and/or services (i.e.: Australia, Canada and the US Navy) that do long-distance missions over large, unpopulated areas (particularly oceans) tend to buy two-engine designs due to the availibility of a second engine if one goes bad. Single-engine designs are better for over-land missions where the reliability of two engines isn't so critical.
Announcement
Collapse
No announcement yet.
Ask An Expert- Aviation
Collapse
This is a sticky topic.
X
X
-
"There is never enough time to do or say all the things that we would wish. The thing is to try to do as much as you can in the time that you have. Remember Scrooge, time is short, and suddenly, you're not there any more." -Ghost of Christmas Present, Scrooge
-
Hey guys random question but hypothetically speaking if you were a billionaire and wanted to buy something like a F-18/15 could you buy from a country that has licensing agreements to build them (Japan F-15/Canada F-18)? Or is it just like buying any "new" US fighter where it's a big fast no even if another country purchased them (F-111 comes to mind)?RIP Charles "Bob" Spence. 1936-2014.
Comment
-
Originally posted by 85 gt kid View PostHey guys random question but hypothetically speaking if you were a billionaire and wanted to buy something like a F-18/15 could you buy from a country that has licensing agreements to build them (Japan F-15/Canada F-18)? Or is it just like buying any "new" US fighter where it's a big fast no even if another country purchased them (F-111 comes to mind)?
There are some F-5s and F-104s in the US. Those all came from foreign surplus (Canada mostly) to dodge the sorts of issues the Collings Foundation ran into. I wouldn't count on ever seeing anything newer in civilian hands.
Comment
-
Originally posted by 85 gt kid View PostHey guys random question but hypothetically speaking if you were a billionaire and wanted to buy something like a F-18/15 could you buy from a country that has licensing agreements to build them (Japan F-15/Canada F-18)? Or is it just like buying any "new" US fighter where it's a big fast no even if another country purchased them (F-111 comes to mind)?
Comment
-
Originally posted by Alpha1 View Postthis doesn't answer why even the F-35 has a non stealthy engine
no such thing as a "stealth engine"
the signature management for the platform is not just about the shape of the nozzles - and the JSF rear end is also IR and signal management. Signal and signature management is not just about nozzle shape, its about an all aspect sig measurement or IR measurement from likely angles of attack and how you diffuse/disrupt/deter/degrade red sensors
the nozzle shapes are all about how they play a part in the platforms ability to manouvre across various ranges - and TVC as in the F-22 is about an emphasis to energise manouvre in the vertical axis (ie to the planes centreline and horizon at any given moment)
a "non stealthy" engine would be one such as a pod hanging below a wing without any heat shield around the nozzles and without the benefits of body shape management. note that every manned and unmanned publicly displayed image of a VLO/LO platform shows different techniques in signature management - the US literally has improved and changed the way it manages signature issues at every generation
what that also emphasises and what seems to get missed by a whole pile of "pseudo experts" in the broader magazine and blogosphere is that VLO/LO is not a fixed construct - its not a single identtity or "feature" that can be countered at one generation of asset and works from that point on.
"stealth" is one of the most overtalked and misunderstood capabilities around IMO
Comment
-
Yea that's what I thought. I knew it was easier to get Migs and Sukhois then US planes but figured I'd ask. I always thought it'd be cool to have someone make a clone of a Tomcat/Warthog (obviously built different then military ones so to avoid issues) but that'd have to be a big lottery :DRIP Charles "Bob" Spence. 1936-2014.
Comment
-
Originally posted by jrb1537 View PostThere are some F-5s and F-104s in the US. Those all came from foreign surplus (Canada mostly) to dodge the sorts of issues the Collings Foundation ran into. I wouldn't count on ever seeing anything newer in civilian hands.
Comment
-
This is a general aviation question.
I was just browsing Wikipedia (some people browse youtube, I browse wiki) and I came across the engines used in light aircraft like Pipers. I noticed the Piper Seneca uses 2 flat-6 engines with 220hp @ 2800rpm each. The displacement is 5.9L.
Continental IO-360 - Wikipedia, the free encyclopedia
My question is why such huge displacement for such low power rating? Is it possible to use more modern auto engines with higher power ratings with less displacement? Or even use some tricks in auto engines to boost power in these aero engines?"Only Nixon can go to China." -- Old Vulcan proverb.
Comment
-
Speaking as a car nut the motor is very light for its time. The weight for my windsor is around 500 lbs and that same motor in the 60s made like 150hp so it's power to weight ratio is my guess why they used it.. Now a newer turbo four cylinder would be great in that :).RIP Charles "Bob" Spence. 1936-2014.
Comment
-
Originally posted by gunnut View PostThis is a general aviation question.
I was just browsing Wikipedia (some people browse youtube, I browse wiki) and I came across the engines used in light aircraft like Pipers. I noticed the Piper Seneca uses 2 flat-6 engines with 220hp @ 2800rpm each. The displacement is 5.9L.
Continental IO-360 - Wikipedia, the free encyclopedia
My question is why such huge displacement for such low power rating? Is it possible to use more modern auto engines with higher power ratings with less displacement? Or even use some tricks in auto engines to boost power in these aero engines?
I used to regularly fly in a Cessna Super Skymaster that had two Conti O-360's in it (technically, IO-360's, actually); we used to rebuild them every few years, and one thing I noticed about aero engines is that they are "over-square", that is, the bore is greater than the stroke of the piston. IIRC, these engines wouldn't go much over 2,500 rpm. I suspect that aero engines, as opposed to vehicle engines, are optimized for reliability, rather than output, hence the rather pedestrian performance figures; losing your engine on the freeway means you just have to pull off the road; losing your engine in an aircraft is a bit more problematic.
The most efficient engines I've heard of being used in aircraft were actually rotary ("Wankel") engines; their power-to-weight ratio was (is?) phenomenal."There is never enough time to do or say all the things that we would wish. The thing is to try to do as much as you can in the time that you have. Remember Scrooge, time is short, and suddenly, you're not there any more." -Ghost of Christmas Present, Scrooge
Comment
-
In addition to weight there are a couple other factors at play as well.
For one, cars and aircraft tend to have different operating patterns for the engines. Cars will rev up to 60-70% power for a few seconds as they accelerate onto the highway, and then sit down around 15-20% as you cruise along. Aircraft engines often run near full power the entire flight. The engine in your car wouldn't last very long if you had it running flat out all the time.
The second issue is RPM. The equation for Horsepower is (HP = Torque x RPM ÷ 5252) yet the prop on an aircraft is generally limited to about 2500 rpm. If you want more power, and you can't increase the RPM, you have two options. You can put in an high RPM engine and add additional hardware to gear it down before it gets to the prop, or you can increase the torque the engine produces.
It would appear that building a large displacement engine that runs at a low RPM with lots of torque generally provides a better mix of reliability, weight, and performance than utilizing the kind of engine you might find in a car.
Comment
-
Ah very good. I knew I was missing something. Thanks guys.
More question about reliability. Modern auto engines are extremely reliable already. How much more reliable are aero engines?
I had some suspicions on the difference between the load on a car engine and an airplane engine. Modern auto engines generate greatest power at high RPM. They still generate, probably greater than 90% of rated max power, at relatively low 2800 RPM. I wonder how much load there is on an engine driving a 2-blade or 3-blade prop at 2800 RPM, compared to a car cruising at 2800 RPM?
How about weight? Are aero engines really that much lighter than an auto engine with smaller displacement?
How does an air-cooled flat aero engine shed heat fast enough idling on the ground?"Only Nixon can go to China." -- Old Vulcan proverb.
Comment
-
Originally posted by gunnut View PostHow much more reliable are aero engines?
For instance, the aircraft engine I was mostly exposed to was the Continental IO-360 (and an occasional radial engine), and they had TWO distributors (on aircraft engines they're called magnetos, since they operate a little differently than a distributor), and TWO spark plugs per cylinder, partly for improved combustion, but also in case one of the magnetos went bad you'd still have another set of spark plugs working. I remember one of the pre-flight checks we did was switch the magnetos on and off, one at a time, to make sure they both worked.
Also, if you've ever looked closely at an aero engine, you will notice that ALL of the fasteners (nuts & bolts) have safety wire going through them to keep them from coming loose in-flight.
Originally posted by gunnut View PostHow about weight? Are aero engines really that much lighter than an auto engine with smaller displacement?
How does an air-cooled flat aero engine shed heat fast enough idling on the ground?
There is often an issue with engines overheating on the ground; usually, there is enough airflow over the engine from the propeller (particularly with radial engines) to keep the engine cool, but I know the rear engine on the Skymaster often overheated on the ground (particularly on hot days) because it wasn't getting enough airflow (the front "tractor" propeller didn't provide enough airflow to cool both engines while on the ground; the rear engine was cooled by "ram" air flowing over the fuselage in flight). Most aircraft are equipped with what are called "cowl flaps", which control the flow of air over the engine to keep it cool; normally, when operating on the ground, the cowl flaps are open, allowing the maximum amount of air to flow over the engine (unless it's already below zero and you're trying to get the engine warmed up!). At cruising altitude and speed, they are normally closed to keep the engine operating at the most efficient temperature.Attached Files"There is never enough time to do or say all the things that we would wish. The thing is to try to do as much as you can in the time that you have. Remember Scrooge, time is short, and suddenly, you're not there any more." -Ghost of Christmas Present, Scrooge
Comment
-
Originally posted by Stitch View PostI will try and answer this one as best as I can.
I used to regularly fly in a Cessna Super Skymaster that had two Conti O-360's in it (technically, IO-360's, actually); we used to rebuild them every few years, and one thing I noticed about aero engines is that they are "over-square", that is, the bore is greater than the stroke of the piston. IIRC, these engines wouldn't go much over 2,500 rpm. I suspect that aero engines, as opposed to vehicle engines, are optimized for reliability, rather than output, hence the rather pedestrian performance figures; losing your engine on the freeway means you just have to pull off the road; losing your engine in an aircraft is a bit more problematic.
The most efficient engines I've heard of being used in aircraft were actually rotary ("Wankel") engines; their power-to-weight ratio was (is?) phenomenal.
Comment
Comment