-TERRAIN VEHICLE Gyrocopters prove their mettle in a hazardous environment B Y I A N J. T W O M B LY P H O TO G R A P H Y B Y C H R I S R O S E F rank Nierhoff is as anxious as a new parent. He's made a number of highspeed taxi runs and the problem persists. The local mechanic, Genro, gets out the differential pressure tester and gets to work. It's a scene played out at shops all around the United States, except that Nierhoff is German and we're in Aranjuez, Costa Rica. aopa.org/pilot AOPA PILOT | 67http://www.aopa.org/pilot