The CT/4C

[Dave Homewood]

Back in 1991 the CT/4C ook to the air and was flight tested. It was a turbine engine powered version of the CT/4 and was based on the borrowed airframe of NZ1940 from the RNZAF (registered as ZK-FXM for testing the concept).

It was hailed as a great success, and I recall seeing it demonstrated at the Hamilton airshow in 1991, where it proved to be very fast and very quiet, compared with the CT/4B.

I was wondering why no further examples have been built since. All the newer Airtrainers reverted to piston engines. Is it something to do with cheaper running costs? Or was there a bigger problem with the CT/4C? I recall a lot of talk in 1991 of the RNZAF considering upgrading to the CT/4C turbine trainer as a better lead in to the Maachis. I was surprised to hear they went to piston CT/4E's in the end.

[vgp]

wiki: CT/4C: A turboprop variant, rebuilt from an RNZAF CT/4B, that never reached production. After a successful flight-test programme and unsuccessful marketing programme the prototype CT/4C was returned to CT/4B standard. i.e NO Sales.

en.wikipedia.org/wiki/PAC_CT/4

CT/4D: (aka CT/4CR) A proposed retractable undercarriage model that has never flown.

[flyjoe180]

I seem to recall that the CT-4C was developed as a competitor for a USAF requirement. Just a thought, but maybe with the loss of that potential US deal, PAC thought it easier to stick with piston engines for countires with smaller training budgets?

[Dave Homewood]

Possibly, and yes it was used in that competition. But I do know that the turbine powered CT/4 was on the drawing board long before 1991. I was shown some drawings by Pat Monk that he'd done while at PAC that featured a turboprop engine and he left that company in the late 1970's.

By the way, was I describing it correctly as a turbine engine? I read that on a site, but to me a turbine sounds more like a jet engine. Is it meant to be turboprop? Is there a difference? I've never worked it out. And is there a difference in jet and turbojet. You sometimes see the latter written. Me? I'll stick to radials and inline V-12's...

[flyjoe180]

A turboprop is simply a gas turbine engine driving a propeller through a reduction gearbox. In a jet engine exhaust gases are used for thrust. In a turboprop the gases are used to drive a shaft. Not much of the exhaust is typically used to provide thrust.

[Bruce]

The USAF requirement was slightly later than the CT-4C experiments, and this was what they developed the E model for (the competition was to replace the USAF slingsby trainers, eventually won by Grob)

You are indeed correct describing the engine as a turbine. The Allison 250 is a turboprop, belonging to the family of gas turbine engines that includes Turbojets and turbofans as well. Turbojets and turboprops also have the sub types of Centrifugal flow (e.g DH Goblin) and Axial flow (e.g RR Avon) or sometimes a mixture of each!
A gas turbine is basically defined as a powerplant that produces motive force by means of (direct or otherwise) of moving gases past a rotary turbine. A ramjet or Pulsejet can be termed a jet, but not a gas turbine as there are no rotating components.... Confused?

[flyjoe180]

And is there a difference in jet and turbojet. You sometimes see the latter written. Me? I'll stick to radials and inline V-12's...

I like V12's too, and big oily radials are always good to watch.

Jet is a term used to describe turbine engines using exhaust gases for thrust. As opposed to turboprop engines which drive a shaft. there are quite a few different types of jet, such as turbojets, turbofans, ramjets, etc.

A turbojet is probably the simplest jet engine. A series of turbine sections provide a straight hrough flow with very little (or none) air bypass (air sent around the compressor sections). Like you see on the old 737 classics and 727's. Or in an A4 Skyhawk. They are efficient at high speeds but lose that efficiency at lower speed and are typically noisy and smoky.

Turbofans are larger diameter engines which use a high bypass of air around the engine core to provide extra thrust and cooling. They are seen on most modern airliners and in modern military engines (they can be afterburned). Turbofans are quieter, more efficient over a larger range of subsonic speeds, and are more economical.

[Dave Homewood]

Thanks chaps.

As for the USAF trials, yes you're right bruce, it was indeed later and now that I think about it rather than an RNZAF CT/4 I think they hired back ZK-DGY and fitted the new engine, didn't they? And it was painted in a gawdy red white and blue US pagentry type scheme, looking like it was on its way to a Thanksgiving parade or something like that.

[FlyNavy]

www2.ku.edu/~kunrotc/academics/180/Lesson%2011%20gas%20turbine%20theory.ppt

1.9Mb PowerPoint file (.ppt) that gives a good overview.

[vgp]

The Contender for the USAF Contract for UPT Screening were the CT-4C & CT-4E - both came into being to meet the specs/requirements set out in that particular contract/competition etc, the PAC CT-4's lost out to the Slingsby T-3A Firefly in which case the T-3A were all grounded in 1997 /stored and finally scrapped in 2006 because it had a habit of killing student pilots and instructors e.g engine malfuncations, spin procedures etc and due to the cost of modifying them also would of been too much to keep them flying.

en.wikipedia.org/wiki/PAC_CT/4
en.wikipedia.org/wiki/Slingsby_T-67_Firefly

the CT-4E was the Airtrainer type mentioned in waikato times at the time as the USAF Contender.

[madmac]

The CT4C was for Thai requirement, to replace the fantrainer which was a bit of a failure. But a revolution removed, killed or promoted to government the backers of the program and in doing so killed the requirement.

I understand it was completely uncertifiable in the as flown configuration due to stability issues (it needed larger tail feathers) this is also why it was limited to 350 hp. But it was apparently a hell of a lot of fun for aero's.

[hardyakka]

I was wondering why no further examples have been built since. All the newer Airtrainers reverted to piston engines. Is it something to do with cheaper running costs?

Once you move up into the turboprop class of training aircraft you come up against a whole new set of requirements and competitors. The CT-4C needed a whole bunch of development and it didn't have the systems and expansion capacity to compete against the PC-9, Tucano etc. (retractable gear, ejection seats etc.)

PAC thought there was a niche for a cheaper turbine trainer, but it seems that once an air force gets to that level of need, price is less important than capability and compatibility with "the next step up".

I got to sit in the CT-4C prototype and make turbine noises as my (then future) father-in-law used to work for PAC. I also remember seeing it flying around Hamilton and how quiet it seemed to be in comparison to the recip model.

The CT-4E was then developed for the competition to provide an aircraft for the US Air Force Academy's Enhanced Flight Screening Program (EFSP). This was to replace the T-41 Mescalero (military version of the venerable Cessna 172). I never really got the straight story on why the CT-4E lost out, but I think it had something to do with the long logistics and maintenance chain back to Hamilton, NZ. (Plus ANZUS ructions, plus "Nuclear Free" issues, plus the "Special Relationship" with the UK and so on)

The Air Force Academy now contracts out flight screening to a civvy company using Diamond DA20s (Same as CTC started out with. I hope USAFA is having a better run than CTC did with them)

[beagle]

flyjoe180 said:

A turboprop is simply a gas turbine engine driving a propeller through a reduction gearbox. In a jet engine exhaust gases are used for thrust. In a turboprop the gases are used to drive a shaft. Not much of the exhaust is typically used to provide thrust.

Pretty sure when I was on 40 Sqn, we were told it, the T56 sent either 300 or 600lbs back out the pipe.

[Dave Homewood]

Thanks everyone for making this all clearer. It's interesting, perhaps the only PAC designed aircraft product to not get anywhere?

[vgp]

oh well quarter of the way right.

[flyjoe180]

Not much of the exhaust is typically used to provide thrust

Pretty sure when I was on 40 Sqn, we were told it, the T56 sent either 300 or 600lbs back out the pipe

Yes that's why I said not much of the exhaust is typically used for thrust. It isn't a feature of most turboprops with civillian power requirements. The Allison (or whatever they call themselves now days) T56 does produce a significant amount of thrust through it's exhaust. I am told this is a significant feature of the Convair which takes a bit of getting used to.

[vgp]

The Air Force Academy now contracts out flight screening to a civvy company using Diamond DA20s (Same as CTC started out with. I hope USAFA is having a better run than CTC did with them)

Making a pilot; the first step

4/8/2008 - PUEBLO, Colo. (AFPN) -- The road to becoming an Air Force pilot begins in Pueblo, Colo., where the Air Force has charged Doss Aviation, a contractor, to provide an Initial Flight Screening course under the Air Education and Training Command.

The purpose of the IFS is to screen aviation candidates and prepare them for the more rigorous flight school programs that will place them behind the most powerful, technologically advanced airplanes in the world.

The course takes on students with a wide range of skill levels from civilian certified flight instructor trained students, to students with no flight time at all.

"Our primary mission here, as the Gateway to Air Force Aviation, is to ensure that our graduates have the attitude, aptitude and motivation to succeed in follow-on pilot training," said Lt. Col. John Tomjack, the 1st Flying Training Squadron commander.

The plane used for the IFS course is the DA-20 aircraft, a $250,000 low-wing plane, armed with a single-engine and a 125 horsepower engine with a maximum altitude of 13,120 feet.

The training site is equipped with a 209,000 square foot building that acts as a miniature Air Force base. The state-of-the-art facility has six flight-rooms and academic classrooms, maintenance hangars, two auditoriums, a shoppette, barbershop, gym, dining facility and an all-faith's chapel.

From day one the students are tested physically and mentally in a high-intensity environment. The first week of class is filled with a tidal wave of academic training. The pressure is purposely applied to measure the student's resolve to complete the course.

"If you pass (IFS), there is a high possibility of you making it through the advanced pilot training programs," Colonel Tomjack said.

2nd Lt. Dylan Rudolph, a student who arrived at the school a week ago said, "It can be overwhelming! Our first academic test is in two days and it covers more than you would normally cover in a whole semester."

"Getting used to terms that flyers use such as pitch and power is hard for somebody who has never flown before," said 2nd Lt. Brandon Magnuson, a student pilot preparing to graduate. "My advice is to press through that first week and learn as much as you can."

Students must also be in excellent physical shape to withstand G-forces associated with the Air Force's supersonic jets. "Physically, students are tested on day one with a fitness test and if they don't pass with an 80 percent or above they are assigned physical trainers and are tested regularly," said Lee Hall, the IFS deputy program director.

The program is set-up for success, but given the nature of the flight screening business not everyone can make it. Since the inception of the 6-week course in October 1, 2006, approximately 10 to 15 percent of the IFS students do not graduate. "It is a very challenging course and you have to come prepared," Colonel Tomjack said.

Ensuring the highest military pilot training standards, IFS has steadily graduated more students each year. In 2006 IFS graduated 350 students, in 2007 there were 950 graduates and 2008, IFS is poised to graduate between 1,300 to 1,800 students.

Students are lodged in a modern facility providing 195 furnished dormitory style rooms, and is considered the largest hotel in the area.

With the proper accommodations in-place, all students have to bring is their motivation and their desire to learn, course instructors said. To graduate from the course they are required to complete 19 sorties and 25 hours of flight time to include two solo flights.

"My favorite part of teaching this course is to see students graduate and become successful pilots," said Greg Dotter, an IFS instructor pilot.

In a week, Lieutenant Magnuson will graduate from this course and is looking forward to flying the T-6 Texan II, the follow-on training aircraft, because of its acrobatic capabilities, he said.

"My ultimate goal is to fly an F-22 Raptor," he said.

If he makes it to graduation, he has a good chance of reaching his goal.

www.af.mil/news/story.asp?id=123093446

[Peter Lewis]

CT-4B Airtrainer c/n CT4-088 entered service with the RNZAF as NZ1940 in 1977. It crashed on t/off Whitecliffs strip, Canterbury, 28May87.

The question I have - was it repaired as a CT-4B after this crash and prior to its conversion to the Allison 250 B17D turbine engined CT-4C ZK-FXM in 1991, or was the damage airframe stored until the conversion took place?

The turbine conversion seemed to have been fairly short-lived, as ZK-FXM was registered to PAC in January 1991 canceled as returned to the RNZAF in June 1992.
When the 4Bs were retired, this aircraft briefly reverted to ZK-FXM before sale to British Aerospace Flight Training, Tamworth as VH-YCQ in February 1999.

[djpacro]

Apr 8, 2008 13:10:53 GMT 12 Bruce said:

The USAF requirement was slightly later than the CT-4C experiments, and this was what they developed the E model for .....

The E was just on the drawing board when the USAF wanted one in the USA to trial so the plan was to borrow an in-service aircraft. The CT-4C was available and I suggested that be sent instead. The 210 hp variant didn't perform very well at Colorado Springs in summer but the USAF was apparently impressed with it.

I had a chance to fly the CT-4C and, as madmac stated "I understand it was completely uncertifiable in the as flown configuration due to stability issues (it needed larger tail feathers) this is also why it was limited to 350 hp. But it was apparently a hell of a lot of fun for aero's." Longitudinal stability was an issue and it certainly needed a larger rudder. Vertical upward rolls were effortless.

PS: Sorry to revive this old thread but I just happened to see this.

[madmax]

Peter, Following its accident in May 1987 NZ1940 was rebuilt at PAC Hamilton and, deemed "surplus to requirements", was placed in storage at, if I recall correctly, PAC Hamilton. Its first flight fitted with the Allison 250 was on 21 January 1991, John Muir was the pilot.
Following removal of the Allison powerplant ZK-FXM, which PAC staff commented was an acronym Fast Experimental Machine, was fitted with a Lycoming AEIO-540 to enable engine cowling molds to be built for the prototype CT-4E ZK-EUN/A19-65 which was undergoing conversion at that time.