Tuesday , 27 June 2017

History

THE VENERABLE MENTOR

“This enduring warbird has become a sought after modernized machine providing tremendous capability with high reliability and low operating costs.”

How many at the Beech Aircraft Factory in 1954 could have imagined that 57 years later the new primary trainers they were building would still be flying, some worth more than the government paid for them at the time.  After a production run that lasted almost 9 years for the piston models, Beech turned out just under 2,000 of the A’s and B’s combined.  Other countries built the plane under co-production contracts and packaged kits.  The US Navy, Marines and NASA still operate the Turbine version (T-34C) for a variety of missions, including primary training, range clearing and chase plane just to mention a few.  Operators in South America such as Argentina, Chile, and Columbia still us the piston A’s and B’s for primary training purposes.  In fact the T-34A has been in continuous use somewhere in the world since the first unit was manufactured in 1953.  No other military training aircraft in history has seen 59 years continuous use by a military agency for as long as the Mentor has.  When future aviation history books are written, the T-34 may be named as one of the greatest aircraft designs of all time along with its GA brother the Bonanza.

Beechcraft, operators and owners owe the success of this timeless classic to one man, Walter Beech.  His visionary design of the Bonanza back in 1947 led to a revolution in the future design of all successive Beech aircraft models.  The Bonanza led to the Mentor, which led to the Twin Bonanza & Travel Air, and that led to the King Air & Baron series still in production today.  Since 1952 the US government has purchased more aircraft from Beech Aircraft Corporation than any other vendor.  The wing design and many components on a 2011 Bonanza, Baron and King Air are identical to those used in production of the Mentor.  Offers have been made to Beech over the years to buy the T-34 Type Certificate but have always have been met with decline because of this model commonality and desire to protect production copyrights.  This large component commonality has led to the ability to constantly upgrade and refine the T-34 over the decades.  Leading to what I call the “Millennium Mentor”.  Generally speaking this would be a fully restored piston powered T-34 A or B with all the latest modifications and upgrades.  Basically creating a 2011 piston powered T-34 with the performance of the Turbine T-34C and operational cost of a new A36 Bonanza.

Very few of the Mentors still flying are in original stock configuration.  Most of the planes have had powerplant upgrades to the Continental 520 or 550 engines and some of the latest restorations and upgrades are using the Continental IO550R overhead induction engine.  This latest STC’d engine conversion puts the aircraft in a new performance category.  The 550R engine is the same as that install in new Cirrus SR22 aircraft.  This engine produces 310+ horsepower and has a TBO of 2,200 hours.

 

T-34B with IO550R Overhead Induction Engine

I have installed this modification in two aircraft so far and can say that it is as close to turbine smoothness and performance as you can get on nickel & dime fuel flows.  With the lower weight of the piston A’s & B’s verses the turbine T-34C you have an aircraft with approximately the same performance in climb and cruise up to 7,000 feet using the 550R engine!  Speed management with the larger 550 engines can be a challenge.  While the C-model has a VNE of 280KTS its older piston brother has an FAA lowered VNE of 219KTS.  The piston models also have a lower gear and flap transition speed of 109KTS.  Dropping the nose while cruising along at 170KTS can easily produce 200KTS in a hurry.  One of the key features of the new engines is the ability to smoothly operate on the lean side of peak.  This yields unprecedented performance such as 150KTS cruise on 11GPH!  This is no trivial matter when flight planning with only 47 gallons useable unless of course you have tip tanks.  With LOP operation on internal fuel tanks the Mentor will provide 450 miles range with reserve. 

Beyond the engine upgrades there are a mind boggling number of avionics changes that can be made.  Many of which are on approved STC lists, as most Mentors are licensed in the standard acrobatic category.  The most popular avionics changes include Garmin 430/530’s and STEC autopilots.  Many owners are opting for glass cockpits weather it be the Garmin 500, Aspen EFD1000 or Chelton EFIS, any of these fit well within the modern sleek looks of the Mentor.

T-34 Instrument panel with Chelton EFIS

Of all tandem seat cockpit trainers the T-34 is in a class of its own ergonomically barring newer multimillion dollar trainers such as the PC7, Tucano or Texan II.  The fuselage width, canopy height and cockpit length provide ample room for even the largest of pilots.  Seats are adjustable and the feel in flight is as if you are wearing the airplane.  Visibility is the absolute best and the plane gives a fighter like feel.  That great feel and performance most likely led to three disastrous crashes by commercial air combat operators from 1999 to 2004.

Prior to these crashes two separate companies, one in Georgia and one in Texas provided the ability for a customer to get in a T-34 and use it as if it were a fighter to engage another T-34 in aerial combat.  Customers who may have had no previous experience as a pilot were given the controls to do what they could in order to engage and ultimately shoot down the opposing aircraft using laser cannons.  Needless to say there was great stress placed upon the group of Mentors used in these operations.  These businesses continued for more than a decade accumulating in excess of 4,000 air combat hours on some of the airframes.  This ultimately led to 3 accidents caused by structural failures from fatigue cracking due to the continued stress of these air combat sorties.  Numerous FAA flight restrictions were placed on all T-34 aircraft during this time.  Eventually leading to 2 AD’s that required reinforcement or replacement of the main wing spar and a reinforcement of the fuselage spar carry through structure.  Even though this type of damage was not seen in any of the fleet operating outside the Air Combat Companies, all owners were required to comply.  Through enormous efforts of T-34 Association and private companies these flight restrictions have been removed and all airworthy Mentors have since been inspected and modified using a variety of the FAA approved structural reinforcements.  The T-34 is no longer used in any kind of air combat type commercial operations today.

The Mentors flying today are vastly stronger than those that rolled off the production line back in the 50’s.  Many of the aircraft are flying with a completely new front end structure to accommodate the higher horsepower engines, factory new Baron wing spars, steel reinforced carry through structures and all new control surfaces made from aluminum skins eliminating the old magnesium.  It is fair to say that the T-34 is the most heavily inspected of all the ex military aircraft flying today.  All of the airworthy fleet have had numerous NDT inspections including eddy current and fluorescent penetrant inspections of critical wing, fuselage, and tail structures as mandated by the AD’s.

This aircraft represents one of the very few true military designs that can be completely rebuilt using mostly new components.  The manufacture still produces skins, actuators, gear components, and major structural components that are useable in the T-34.  Continental produces new engines, both Hartzel and McCauley manufacture new propellers for this model and there are a variety of appliance and component manufacturers that list this model on their STC AML’s.  Other than the core fuselage structure from firewall to tail-cone, the T-34 can be restored to a mostly new aircraft using 90% brand new components.  Not many warbirds can make that claim!  Because of this level of support, the Mentor is an aircraft with an outstanding reliability record.  With this type of reliability and economical operation, many of the owners routinely fly these aircraft 130-150 hours a year.  Annual inspections for this type of aircraft are simple and normally inexpensive requiring no special equipment or components.  Many general aviation maintenance shops have the capability to work on the T-34 and technical support is just a phone call away.  The T-34 Association web site www.T-34.com is a great repository for a wealth of technical information including all maintenance manuals.

Many of these planes have come up for sale now that all of the airframe fixes have been accomplished.  Through these tough economic times of the last few years the T-34 has actually begun to increase in value.  Most likely this is due to its economical operating costs as the price of avgas has remained stubbornly high.  Many warbird operators are buying the T-34 as a second or third airplane.  Prices have ranged from $100K for a completely stock small engine plane to $500K for a ground up restoration having all new components, including the latest powerplant, and avionics.  To do a true ground up restoration takes approximately 5,000 hours and $280K in parts and materials.  All told there are approximately 460 of these planes in the USA.  The FAA registry lists over 400 aircraft, (A’s & B’s mixed) at any given time.  Roughly 270 of those registered are in airworthy status.  There are 70 or so projects out there that could be built up into complete flying aircraft, some of which are still in the Navy’s possession.

 

 The Mentor lives up to its reputation as a trainer and is very easy to fly.  This is most likely the reason for its enduring popularity.  It is easy on the pocketbook, well easier than most other warbirds.  The plane really has no bad flying habits.  Stalls are gentle and straight forward, and with a touchdown speed of 65 KTS very little runway is needed.  The plane is light on the controls and is great for rolls and loops, particularly with the larger engines.  The T-34 may very well be the best of all warbirds when it comes to formation flying.  The unobstructed 360 degree view from the cockpit provides a pilot with a great platform from which to hone the formation skills.  The six cylinder Continental engine will also take the punishment of a student learning formation or acrobatics unlike many of the larger radial engine trainers.  The T-34 does just about everything better than most other planes in its category.  So if you are looking for a warbird that is easy to fly, does good aerobatics, is a great formation platform, has good cross country speed, and is fairly easy on the pocketbook, then give the T-34 a good look you may be pleasantly surprised!

Dan Blackwell Jr.