MAMBA'S FIRST FLIGHTS

Mamba's First Flights

     Jeff Seymour, Mr. SWB, came to the Florida International Jet Rally to participate in the initial flight tests of the Mamba turbojet engine.                                                                                                                                            PPPPPWe installed it in our F-80 Shooting Star that had been powered with a RAM 500. Since it is a 3-1/2" diameter engine, it fit very nicely into the bypass and tailpipe system that is a BVM production unit.
     The electronic control and engine accessories are simple and compact enough to mount on a single 1/8" plywood board for easy installation into the front of the F-80/T-33 models. Similar installation mounts are being developed for other BVM jets like the F-86 and Bob Cat.
     The total installation weight of the engine and airborne components is 3-1/4 pounds which is about minimum for this engine size and thrust class.

     The Mamba and its electronic control system are all new and independently developed by SWB for the model jet market. While it does utilize a turbine wheel from the WREN company and is of course similar in diameter, this engine reflects the technology and precision manufacturing that SWB turbines has become known for as a commercial and military supplier.
     SWB's focus for the past 10 years has been to develop, test and supply turbojet devices including a HISID vehicle, the X-43 and they were involved in the cruise missile program for the military. The success of these ventures has allowed SWB to develop a second division within the company to manufacture turbojet products for the model industry.
     A close look at the Mamba and its control system which was developed by Andy Low is evidentiary of this experience.

     The metal work is superb, the balance perfect and the welding is definitely professional. Other engines in this class have deleted the cone inside the exhaust nozzle for cost reduction reasons, but, to make the Mamba really right, this important fairing is mounted behind the turbine wheel with six welded stainless steel pylons.
     As the hot gases exit the perimeter of the turbine wheel of the Mamba, the cone prevents a pressure dump and properly directs the gases through the nozzle.
     This is just one visible feature of the Mamba that reflects the experienced design philosophy that produced this quality piece. As time allows, I'm sure a more in-depth article on the engine will reveal the secrets of its combustor (the black art) and fuel injector system that are responsible for the Mamba's very rapid acceleration (3 seconds) and fuel efficient operation.

Our flight testing thus far has allowed a few minor adjustments to the electronics to facilitate faster, easier starts in the Florida weather. To test for a lean blow out condition in flight, we rapidly reduced the throttle to idle in a vertical dive multiple times - it passed the test.
The engine will next undergo some tests at a high altitude facility that should ready it for consumer acceptance.

Simple Air Start

     As mentioned before, a Mamba installation is very light in weight which is important for the size of models it will power. Part of this weight advantage is due to its simple, yet completely automatic air start design.
     One has to connect the ECU umbilical to the Data Terminal, then plug in the air and propane tubes. Now, turn on the ECU power switch, check for the "ready" indication on the Data Terminal and you are set to start.
     Switch on the air and the ECU automatically sequences the ignition, propane and kerosene, when the Data Terminal rpm reads 60k, switch off the air. It's that simple.
     We found that a fully charged "pony bottle" (15 cu. ft.) will start the Mamba 12-15 times.
If you don't already own the scuba equipment, we would suggest that you obtain a 40-50 cu. ft. bottle, it is a nice compromise between size and effort to refill it. Such a bottle will start a Mamba many, many times.
     There are very experienced jet pilots who are on both sides of the air start vs. electric start issue. We fly JetCats and AMT's and now the Mamba and what is really important to us is that the systems are reliable and easy on the engine. This Mamba, simple air start, certainly is both.

Economic Operation

There is a case to be made that this size engine will evolve to become a very economical way to enjoy jet modeling. The turbojet engine does not become significantly less expensive as it gets smaller, as a matter of fact, they are more difficult to manufacture.

However, the models, the retract systems, the fuel consumed, the ease of handling and the vehicle required to transport them all are contributing factors.

     The engine's longevity, reliability and the availability of technical assistance are very important factors that contribute to your turbojet purchasing decision.
     At $2,495.00, the Mamba by SWB is not the cheapest in its class, but, it is my belief that it will prove to be the most economic in the long run.     lllllQuality of manufacture and a real company to back it up does have its costs.
     Watch this site for updates on the Mamba's availability.

Bob Violett

A BVM Saber/Fury in an SUV with plenty of room to spare.