TECH II: AIRFRAME & STRUCTURAL SECTION

A primer on the Project's engineering modifications.

JUMO ENGINE CASTINGS

Easily the best known feature of those listed in this section, the precision engine castings were first proposed, then designed, by the late Steve Snyder.  As an aeronautical engineer, Snyder recognized that simply hanging a pair of J-85s on the Me 262 within oversized cowlings would create as many problems as it solved.  Differences in wing root forces, weight distribution, and the Center of Gravity would have completely altered the characteristics of the original Me 262.  His solution may have been borne of necessity, but it has emerged as one of the most innovative engineering feats in the entire effort.

Detailed castings have been made from an original Jumo engine, and all related accessory drive components, gearboxes and pressure lines will be precisely duplicated for surface-mounting.  When the access panels are opened, bystanders will see a historically accurate duplicate of a Jumo 004B engine.  Concealed deep within the casting, the modern powerplant will go all but completely unnoticed.

Perhaps most significantly, the entire assembly (when mated with the J-85) will closely duplicate the nacelle weight of the original Jumo 004.  In this respect, the original performance characteristics of the aircraft will be faithfully preserved.

LANDING GEAR IMPROVEMENTS

As the landing gear was known to be another weak area on the original Me 262, a detailed analysis of landing gear stresses was directed.  This process revealed that a shock loading was generated by the spin-up forces of the large, heavy main wheels, which had to be reacted into by the wing landing gear attachment structure.  This placed a severe demand upon wing spar area and the airframe simply had to absorb these forces.  Over time, this would have had a devastating effect upon the aircraft.

In part, this problem can be traced to the history of the aircraft.  As originally designed, the Me 262 was equipped with a standard tail wheel (in lieu of the nose wheel).

In the tail-dragger configuration, the main gear was bolted directly onto the wing spar; however, the tricycle modification resulted in the creation of a separate wing torque box to be used as a mounting point.  This torque box was susceptible to damage, and very difficult to repair.

On the new Me 262s, this area has been reinforced with additional structural features, and the project is considering additional design changes that may further enhance the safety and longevity of the landing gear.  In addition to the wing box reinforcement, the nose gear mounting point and strut assemblies have been greatly improved.  In short, the entire system has been strengthened by a significant margin above what it was originally.

BRAKE SYSTEM IMPROVEMENTS

The braking systems of wartime German aircraft usually left something to be desired, and the Me 262 was no exception.  Brake fading and/or complete system failures were a common complaint.   (For a brief description of such an incident in American hands, see Ken Holt's narrative on the Watson's Whizzers pages.)

The notoriously ineffective nose wheel brake has been eliminated altogether, although the original brake lines will be duplicated for appearance.  Meanwhile, the  marginally performing drum brakes on the main gear have been replaced by a cleverly-integrated disc brake system. The improved disc brakes have been mounted within the wheel hub assembly itself, and have the capacity to stop an aircraft more than twice the weight of the Me 262.

THROTTLE PRESSURE SPRING (TPS) SYSTEM

Despite the fact that the nacelle weight will be roughly equal to that of the original Me 262, the power available to the pilot has still been significantly improved.  Since the characteristics of the airplane were well known at the 1,800 pound thrust level, every effort has been made to duplicate this performance envelope, and not create some "Super Me 262" class airplane.  Still, the fact remains that the increase in thrust is significant enough to force us to consider some entirely new engineering aspects.

While a positive development in most respects, the added power can present new problems of its own.  For example, an engine failure during a full power takeoff could quickly result in an uncontrollable asymmetric thrust component.  Our project engineers understood this problem, and developed a simple method to control the situation.

To address these issues and provide the pilot an accurate indication of actual power settings, the project has carefully modified the throttle assembly to be fitted with a throttle pressure spring which provides a positive force indication of engine RPM at 1,800 lbs. thrust.  In other words, the pilot will know when the maximum specification thrust levels of the Jumo 004 have been reached.

If the pilot desires additional power, he may push the throttles beyond the spring loaded position, holding them open against this spring pressure.  The actual hard stop for the throttles will be set at the J-85's maximum thrust setting, which is projected to be around 2,400 to 2,500 lbs., as mounted.  The additional power is reserved for two operational regimes.  On takeoff roll, prior to liftoff, and during climb.  Takeoff roll is initiated with full power, but it is then  reduced to the original Jumo takeoff thrust level (1,800 lbs.) just prior to liftoff.  The excess power may be added once safe climb speeds of 260 Miles Per Hour are achieved.

 

© 2001 Sabre Design Group. All rights reserved.