Can you explain the different kinds of aircraft engines?

[PhantomTweak]

I may be wrong, but I'm pretty sure most of the Phantoms had the J-79 in it, not counting the UK birds. I honestly don't know about those. There was a small amount, relatively speaking, of bleed air from the compressor section used for various reasons. Cockpit AC and pressurization, fuel tank pressurization, laminar airflow in the turbine section and tail pipe to keep them cooler, and so on. A "small amount" compared to the total airflow through the engine, that is. Most of the bleed air was from the 17th compressor section. There was more than enough available for what it was used for. But not a lot was used for actual propulsion, as far as I know. That all went through the turbine section as hot gas from the burners.
The Israeli Kfir has the J-79 in it too. Popular engine in it's day.

Have fun all!
Pat☺

[Craig Taylor]

There is no Duke that now has jet turbo props like a Cessna 441, just a version that has turbos added to the piston engines?

I don't think I noticed anyone addressing this question. There is in fact a turbine conversion of the Duke, referred to as "Royal Turbine" or "Duke Turbine" or various combinations. Northwest Turbine LLC and Rocket Engineering Corp of Spokane, WA replaced the piston engines with P&W PT6A-35s, making various other modifications to enable the engine swap. You can read about it on their website here. As far as I know, RealAir are the only ones who made a version of this for FSX. EDIT: Sadly no longer available.

[Sundog]

I may be wrong, but I'm pretty sure most of the Phantoms had the J-79 in it, not counting the UK birds. I honestly don't know about those. There was a small amount, relatively speaking, of bleed air from the compressor section used for various reasons. Cockpit AC and pressurization, fuel tank pressurization, laminar airflow in the turbine section and tail pipe to keep them cooler, and so on. A "small amount" compared to the total airflow through the engine, that is. Most of the bleed air was from the 17th compressor section. There was more than enough available for what it was used for. But not a lot was used for actual propulsion, as far as I know. That all went through the turbine section as hot gas from the burners.
The Israeli Kfir has the J-79 in it too. Popular engine in it's day.

Have fun all!
Pat☺

All of the operational F-4's had J-79s, except the F-4s built in Britain, they used the RR Spey. However, they did end up flying some US F-4Js for awhile. {url=https://en.wikipedia.org/wiki/No._74_Squadron_RAF}No. 74 Squadron[/url].

[hairyspin]

Bypass air should not be confused with bleed air - all jet engines use bleed air to keep the flame off the metal etc. Turbofans in fighter jets have better low speed performance, so the J79-fitted Phantom was faster in level flight but the Spey-equipped ones took off and climbed better. Turbofan-equipped Tomcats don't need afterburners for carrier takeoff and climb out, significantly increasing their operational range. All from using the engine power to blow extra air out the back.

[simondix]

In reply to a subsequent question of piston prop aircraft being converted to turboprop or jet engines. There were the Basler, Braddick and Dart DC3's. The Conroy Mustang and I believe a Vickers Viking became a jet testbed.

[DaveB]

Yup.. the Viking had a pair of Nene's strapped one under each wing! An unlikely looking jet for sure but it set a passenger aircraft speed record from London to Paris!! Unlike many test aircraft.. the Viking was converted back to props. There was always a hope that one of the team at CBFS would take it on for FS9 but data on it was scarce.

ATB
DaveB

[Dev One]

Trent Meteor.......1st propjet aircraft.

[guitar0633]

Love reading the discussion guys, thanks. When I was a boy I used to get my older brothers talking about baseball and football and I could just sit for hours and hear them tell stories about their baseball heroes and memories. It's the same with places like the Sim OH. I love getting some of you knowledgeable guys started talking and giving up your experience and knowledge so I can just kick back and read about it all. Much more fun somehow that watching YT vids. I like those too, but there's just something interesting in reading the thoughts from smart guys like the aviation lovers here.

Thanks again.

[Bjoern]

No mention of the Convair 580, the most successful conversion from piston to turboprop?

The title of reengining queen shall be taken by the Douglas DC-8. Turbojets to low bypass turbofans to high bypass turbofans. The latter squeezed another good 20 years of use out of a design hailing from the late 1950s.
To be fair, some KC-135 models also deserve the title, going the exact same route but being exclusive to the military.

Bypass air should not be confused with bleed air - all jet engines use bleed air to keep the flame off the metal etc. Turbofans in fighter jets have better low speed performance, so the J79-fitted Phantom was faster in level flight but the Spey-equipped ones took off and climbed better. Turbofan-equipped Tomcats don't need afterburners for carrier takeoff and climb out, significantly increasing their operational range. All from using the engine power to blow extra air out the back.

Tomcats were never equipped with anything but turbofans. With the original TF-30s, they were a bit underpowered, requiring afterburner takeoffs and were prone to flameouts. The later F-110s were reportedly the single best aircraft improvement in history with all that power and reliability.

Might want to mention that the bigger intakes and larger frontal area of the Speys (more area = more drag = less effective thrust) were the reason for the reduced top speed. And that the afterburner weakened the carrier deck due to the heat.

[hairyspin]

...And that the afterburner weakened the carrier deck due to the heat.

Made a mean burger, though...

[Bjoern]

If you want a real oddball of a jet engine, look no further than the RB.199 from the PA200 Tornado. Consider that normal military aircraft engines are built for simplicity, with two independent compressor and turbine sections (spools) at best for at least rudimentary efficiency and as much power as possible. And most modern engines are built with a bypass (turbofan) to increase mass flow through the engine (increasing available power) and to provide laminar air flow for cooling along the engine walls. The burner section in more modern engines is trimmed for reliability and the afterburner section is quite long to ensure proper combustion of the additional jet fuel. And there's a (flexible) nozzle with a shrinking and then expanding diameter to make the best use of the kinetic energy in the exhaust gases for maximum power.

Now you've got the cheeky little, multinational bugger in the Tornado. First, it's a turbofan, which is good and as normal as it gets with this engine. But unlike its brethren, it's a turbofan with three(!) independent compressor and turbine sections (triple spool). First oddball property. Triple spools are only found in Rolls' other modern civilian engines like the RB.211 (think TriStar, 747 and 757) and beyond. The reasoning behind this is that three spools have each compressor section rotate at its optimal velocity throughout its envelope, providing maximum efficiency in compression - in theory. Practically, during power changes, trying to get three independent compressor sections is like trying to get three kids to do chores. The eldest (high pressure section) does what you tell it to without much hesitation, but while you try get either the youngest (low pressure section) or the middle one (middle pressure section) to join in, the other of the two will smply do what it pleases. To the effect that, in the worst case, the chores won't get done as quickly as they should or, worse, that the entire process will momentarily break down. Yep, that's an operational limitation right there. One other property of three spools is a very elaborate system of lubrication because oil rules the world and everybody hates friction. In their infinite wisdom, the engineers devised a bearing and lubrication system that's only really tight at high rotation speeds, meaning that part of the engine oil takes a stroll into other engine compartments at lower power settings. When seeping into the turbine sections, it causes a mild case of combustion visible as smoke and the blackened vertical stab so typical for the Tonka.

Continuing the theme of inefficiency and oddballness, the fuel injectors in the combustion chamber inject fuel in the opposite direction of the air flow. No elaborate mixing into the direction of the flow to optimize things like in other engines, just a simple "Here's fuel, here's air, now sort yourselves out" to keep the combustion chamber as short as possible. Efficient? Not quite.

The turbine section ties a into the compressor section above, but it isn't really special. The exhaust gas bumps into the turbine rotors, basically converting a bit of velocity and pressure into rotational energy and thus driving each of the three shafts and its attached compressor section. Standard, yawn, NEXT.

Aaaand it's the afterburner, which, for a military jet engine is SHORT. So short, in fact, that the reheated exhaust gas doesn't have much time to cool down and expand, giving the Tornado its characteristic blue afterburner flame and the heat signature of an B class star. It's said that a Tonka in afterburner can be spotted with the bare eye from Proxima Centauri and that the only usable countermeasure is a tow array for an O0 (o zero) supergiant star.

As if the intense heat of the exhaust is not bad enough, the nozzle adds insult to injury because it totally does away with the standard shape of tighten-widen and just tightens, essentially trading some thrust for mechanical simplicity (shoulda simplified the compressors instead, eh?). The nozzle, however, still widens to accomodate the added exhaust gas flow when in afterburner, so it's got that going for itself, which is nice.

Just when the exhaust gas thought it was clear of this rollercoaster ride among engine construction, it slams right into the thrust reverser panels, the last oddball characteristic of the 199. The Swedes thought that putting thrust reversers on military aircraft was a superb idea because it saves some poor conscript from having to handle the mess of nylon and lines called a braking parachute or blowing on superheated brakes, so Fritz, Giovanni and Lord Mc Lordface ran the numbers and came to the conclusion that it was perfect to offset the horrendous R&D costs for getting the compressors (again: THREE SPOOLS!!!) to work by reducing the number of required wheel brake changes. Great thinking, folks! What the three musketeers didn't realize, however, is that the exhaust gas gets super miffed at being thrown out in the opposite direction it came in and therefor will merrily deposit anything remotely sooty (lubricant, partially burnt fuel) on any surface of the aircraft it can find - most prominently the vertical stabilizer. This is the reason why any Tornado looks worse than most Air France airliners and why there's absolutely no point in cleaning them around the tail end. Rumors have it that a good number of Tonkas still carry 30+ year old reverser marks...

And this concludes the general oddities about the RB.199. I didn't dive into the minor ones (the starter comes to mind...), but this shall do.
To recap, this bit of drunk powerplant engineering has a very complex compressor prone to hiccups, leaks oil at low RPM like the Exxon Valdez, has inefficient combustion (how they got it smoke free is a mystery to this day), the heat signature of the surface of the sun and a "no tractor needed" reverse gear.
On the upside (yes, rumor has it that these exist), it doesn't need any additional mechanical devices to optimize the flow through the compressors because of the three spools, it's compact, has a good power to weight ratio, a device to shorten the landing roll, hyper ultra awesome blue afterburner flames and an exceptionally sweet sound and noise level. Oh, and its concept's been proven and working for 40+ years by now.

But it's so odd when compared to the other engines, I can't help but love it.

[PhantomTweak]

The F-14's were permitted minimum AB take-offs from shore stations, if really necessary, but not the ships, and no max AB take-offs from anywhere. If they had a flame-out during an AB cat shot, it would cause an un-recoverable yaw moment. Get that on a cat shot, it's all over. Probably all over the bow of the boat.
The engines, in AB, had enough power, far enough off to the side of the plane's centerline, that if one quit, but the second kept running, again, in AB, the plane would start to do a flat spin then and there, no matter how much rudder the pilot input. Grumman even stated the F-14 wouldn't do a flat spin, no matter what, at first. But after loosing a few to flat spins, they changed the NATOPS. No corrective action to a flat spin under any conditions, other than EJECT. Top Gun got that right in the movie anyway.
I can copy the entries from the NATOPS about all this...

The F-14 is a still a fun as heck plane to fly though! Especially if it's modeled with the TF-110 engines, as in the D model '14s. Better than 1:1 thrust to weight, which fighter pilots had been dreaming of since jets came about. Understandably!

Have fun all!
Pat☺

[SkippyBing]

And this concludes the general oddities about the RB.199.

I'm not sure if it's unique to the RB.199 but there's also an arrangement where if electrical power is lost it goes to full throttle. Great if you're airborne and need engine power while you sort out the electrical gremlins, not so much if you're overly enthusiastic getting out of the aircraft at an airshow and get ahead of yourself during the shut down checks. Cue the entire crowd ignoring the flying display and looking towards the increasingly high pitched whine coming from the parking area followed by bits of engine being liberally spread across dispersal.
Took them a couple of weeks before it was ready to be flown out.

[lazarus]

Other oddball turbofan's, the GE CJ-805 and CF-700 aft-fan engines, with an LP turbine at the back driving a nifty transonic fan, with attendant hot gas and oil leakage.
One class of engine not mentioned as it dead-ended-for now-are the compound-turbines, like the Napier Nomad's. A 41.1L/2502 cubic inch H-12 supercharged diesel engine/gas generator driving half a contra-prop and an axial 3-stage turbine/12-stage compressor set that drove the centrifugal supercharger and the other half contra-prop through a combining gearbox. In case this monstrosity failed to provide enough diversion for the fitters, an afterburning system injected more fuel into the turbine on take off. It weighed four and a half thousand pounds, had more moving parts than a box-car full of swiss watches and was highly temperamental on a good day. When it all ran in the same direction at once, it gave 4000 hp/320 lbf at take off, but it's cruise fuel consumption was an amazingly low 0.36 lb/hp/hour@3030hp in cruise.
The Nomad II cut the turbine-propeller gearbox and afterburning for a simplified turbine-compound blowing the diesel and hydraulic clutched to the diesels crankshaft, chopping 1000 pounds and removing most of the gremlin nests.
Nomad II: max take off at a staggering 208" hg boost-4100hp/320lbf thrust.
Cruise sfc @ 11000ft/300kts/3030hp: 0.345 lbs per equivalent horsepower per hour. An unsurpassed SFC. However, the devil is in the details.
Jets burn more fuel, but are (mostly) lighter and simpler, and go faster. The reduced chock to chock times give a comparable average sfc for long distance flight.

[DaveB]

Might want to mention that the bigger intakes and larger frontal area of the Speys (more area = more drag = less effective thrust) were the reason for the reduced top speed.

That was a necessary trade-off for the much improved low altitude performance required to get them off our tichy carriers. Not ideal I know but needs must!
ATB
DaveB

[Bjoern]

The F-14's were permitted minimum AB take-offs from shore stations, if really necessary, but not the ships, and no max AB take-offs from anywhere. If they had a flame-out during an AB cat shot, it would cause an un-recoverable yaw moment. Get that on a cat shot, it's all over. Probably all over the bow of the boat.
The engines, in AB, had enough power, far enough off to the side of the plane's centerline, that if one quit, but the second kept running, again, in AB, the plane would start to do a flat spin then and there, no matter how much rudder the pilot input. Grumman even stated the F-14 wouldn't do a flat spin, no matter what, at first. But after loosing a few to flat spins, they changed the NATOPS. No corrective action to a flat spin under any conditions, other than EJECT. Top Gun got that right in the movie anyway.
I can copy the entries from the NATOPS about all this...

The F-14 is a still a fun as heck plane to fly though! Especially if it's modeled with the TF-110 engines, as in the D model '14s. Better than 1:1 thrust to weight, which fighter pilots had been dreaming of since jets came about. Understandably!

Too lazy to dig up "Bye,bye baby!" and find out who to credit for the technique, but with enough altitude remaining, a flat spinning F-14 can be recovered by manually sweeping the wings to 68 degrees, thus moving the center of lift aft which will drop the nose. Not sure if this ever trickled down to the squadrons and if it saved some unfortunate butts, but at least the spin wasn't a guaranteed killer.

I'm not sure if it's unique to the RB.199 but there's also an arrangement where if electrical power is lost it goes to full throttle. Great if you're airborne and need engine power while you sort out the electrical gremlins, not so much if you're overly enthusiastic getting out of the aircraft at an airshow and get ahead of yourself during the shut down checks. Cue the entire crowd ignoring the flying display and looking towards the increasingly high pitched whine coming from the parking area followed by bits of engine being liberally spread across dispersal.
Took them a couple of weeks before it was ready to be flown out.

First time I've heard about that quirk. Neat!

[PhantomTweak]

Too lazy to dig up "Bye,bye baby!" and find out who to credit for the technique, but with enough altitude remaining, a flat spinning F-14 can be recovered by manually sweeping the wings to 68 degrees, thus moving the center of lift aft which will drop the nose. Not sure if this ever trickled down to the squadrons and if it saved some unfortunate butts, but at least the spin wasn't a guaranteed killer.

Thanks for the info, Bjorn!
Not that I'm an expert by any stretch, but I've never heard of that. I don't know how easy it would be though.
The pilot, who is the only one that has control of the wing-sweep, as far as I know, might have some trouble reaching the control. There is a fair amount of what they call "eye-balls out" force involved during a flat spin, and the pilot has it worse than the RIO, who is a lot closer to the center of rotation. It would tend to pin the pilot forward in the harness, arms against the cockpit side-walls, preventing him from reaching the controls, or either ejection handle. Unless he was fast and got things done before the spin developed very far. One of the few things about aircraft Top Gun got right.
Doesn't mean no one ever did it, just means the pilot would have to recognize the impending spin and react to it very quickly. As far as I know, though, the NATOPS just says FLAT SPIN--EJECT, in the Emergency Procedures section. No qualifiers, altitude limits, speed on entry, anything. Just jettison the aircraft. And if it has developed much past the beginning stages of a flat spin, the RIO is going to be doing the ejecting.
Fun times

Might be something interesting to try in Dino's F-14 in FSX...
Pat☺

[Bjoern]

Thanks for the info, Bjorn!
Not that I'm an expert by any stretch, but I've never heard of that. I don't know how easy it would be though.
The pilot, who is the only one that has control of the wing-sweep, as far as I know, might have some trouble reaching the control. There is a fair amount of what they call "eye-balls out" force involved during a flat spin, and the pilot has it worse than the RIO, who is a lot closer to the center of rotation. It would tend to pin the pilot forward in the harness, arms against the cockpit side-walls, preventing him from reaching the controls, or either ejection handle. Unless he was fast and got things done before the spin developed very far. One of the few things about aircraft Top Gun got right.
Doesn't mean no one ever did it, just means the pilot would have to recognize the impending spin and react to it very quickly. As far as I know, though, the NATOPS just says FLAT SPIN--EJECT, in the Emergency Procedures section. No qualifiers, altitude limits, speed on entry, anything. Just jettison the aircraft. And if it has developed much past the beginning stages of a flat spin, the RIO is going to be doing the ejecting.
Fun times

Dug through the book* again, but couldn't find anything. I swear I saw it in there, though.

However, and albeit copied from another website, this article explains it pretty well:
http://combatace.com/blog/5/entry-19...spin-recovery/

Might be something interesting to try in Dino's F-14 in FSX...

I doubt it can be spun. Besides, being a "D" model, it doesn't have any reason to.

There are some videos for spin recovery techniques for the Aerosoft F-14A though.



*Not that it's a bad book. If you want to read a 200 page love letter to an aircraft, there's no way around it.
https://www.amazon.com/Grumman-F-14-.../dp/0760325766

[Victory103]

Beat me to it Bjoern, good post and answers the question. Also agree that Dino's "D" and all late model A/Bs had Digital FCS added, but you can spin the Aerosoft Cat model just fine.


For Pat, it's the B/D's with the GE F-110 motor that have the NATOPS warning about AB on take-off, the original and "not designed for the Tomcat" PW TF-30 allows AB take offs.

Guess no one wanted to take a stab a helicopter turboshaft engines?

[Bjoern]

Guess no one wanted to take a stab a helicopter turboshaft engines?

Turboprops with comparatively slow spinning propellers.

[SkippyBing]

Turboprops with comparatively slow spinning propellers.

Spot on. ~55,000 RPM down to ~360 RPM makes for a big gearbox!

[bbrz]

Spot on. ~55,000 RPM down to ~360 RPM makes for a big gearbox!

? which engine is that if I may ask?

[hairyspin]

A difference between helicopter turboshaft engines and many turboprop or turbofan engines is the turbine powering the helicopter rotors is often a free turbine. This means it's not mechanically connected to the gas turbine sections, it's instead driven only by the hot gas exiting the gas turbine. Watch a typical turboshaft-powered chopper from startup to lift-off and you'll hear the gas turbine start (accompanied by regular sparking sounds), run up to speed and sit there warming until the free turbine engages. The rapid speed-up of rotors to flying speed used to baffle me until it was explained.

[Mach3DS]

The same thing can be seen on an aircraft turboprop. If the exhaust pipes are at the front, it's typically an air coupled or free turbine. Meaning there is no mechanical linkage to the drive assembly other than exhaust gases. This is what is the primary reason for slow power conversion when running at Low rpm and then going quickly to high power....usually have to wait a few seconds for the air coupled to kick in.

[Bjoern]

These are a bit long, but seem to get the point between fixed and free power turbine along quite nicely.

https://www.youtube.com/watch?v=As-NZ5t8sxY

https://www.youtube.com/watch?v=8A2yr3ALt6c