GIV Drift Up
I am writing this story as a reminder about how much damage an ignorant instructor force can do. The lesson is that just because a person of “authority” says something, doesn’t make it true. A bit of context first. My progression of Gulfstream time is like this:
GIII (AC)
GIII (DC)
GV
G550
GIV
G450
I spent a lot of time in the GIII and GV, very little in the GIV. That meant I didn't have to suffer through the growing pains of the GIV community and by the time I got to the GIV, I was ready to deal with a lot of the nonsense.
If you look at this photo, imagine you are at altitude halfway across the pond. Selecting the S.E. Fixed Alt Crz page gives you the correct drift down speed (DRIFT DN SPD .77M) and the altitude you can expect to descend to to maintain altitude on one engine (S.E. CRZ FL191). All that is great. If you don't lose an engine, hours later, as you've burnt off considerable fuel and started your descent you select the same screen, the right photo. Now it gives you a "drift up speed" (DRIFT UP SPD 198) and altitude (S.E. CRZ FL279). Of course there is no such thing. If you were still at altitude at this reduced gross weight these numbers would be a good drift down speed and altitude. The designer of the screen didn't understand the purpose of the number and simply reasoned it has to be "Drift Up" since you are below the altitude. That is obvious to anyone with a good understanding of two-engine jet performance. Which makes the following story understandable . . .
When SimuFlite came along, those of us raised at FlightSafety were skeptical but then we realized the best thing to ever happen to FlightSafety was SimuFlite. The newcomer forced the old head to improve. But I continued to spend most of my time with FlightSafety until I found myself at SimuFlite for GIV initial. In the simulator I was with a fairly new and timid instructor who often gave me instruction as if asking my permission. The first assertive thing she ever said to me was,
"Drift up, James."
"Whaaa?" It wasn't my most articulate response, but when confronted with lunacy I guess I am tempted to respond in kind.
"Once you've retracted the flaps after an engine failure," she said from the jump seat, "you need to fly drift up speed.
"I am flying VSE," I responded while pointing to the display controller, "just like the book says."
"Yes I know," she said, "but after VSE you fly drift up."
"Show me."
With a few button presses she brought up the aircraft's single engine performance page, something we didn't have in the GV. It clearly said "DRIFT UP SPD" and had a number which was quite a bit higher than VSE. So I pushed the nose down and accelerated, wondering what part of aerodynamics I had slept through in college. Fortunately this was Friday and I had until Sunday before my next simulator. I spent all day Saturday looking for something, anything, about drift up. Even the GIV manuals were silent on the subject.
For the Sunday simulator, while in the right seat, I snuck a peak at the offending page, it said DRIFT DN SPD. The speed agreed with the book value for drift down and it showed the correct drift down altitude as S.E. CRZ. As the hour progressed, I keep sneaking a look at the page and realized that as the airplane flew below drift down altitude, the DRIFT DN turned to DRIFT UP. I've spent a fair amount of time over the years programming computers and can recognize a mistake from a programmer that doesn't know the first thing about flying. That's what this had to be. The programmer thought you shouldn't drift down to an altitude that is above you, so DN became UP.
After we swapped seats I waited eagerly for my next engine failure. I dutifully cleaned up the aircraft and zeroed in on VSE.
"James," the instructor said as if on cue, "don't forget drift up speed."
"I don't believe in it," I said, "and telling anyone to fly that speed jeopardizes the safety of the airplane, violates the flight manual, and I am not going to do it.'
She said nothing. Not even during the debrief. My sim partner kept silent as well, perhaps feeling his type rating was in just as much jeopardy as mine.
The next morning I was greeted by the center manager and the senior GIV instructor. The center manager was somebody I knew at Andrews, the same Colonel C from the That Looks About Right story. He and I turned into long time friends and he usually treated my academic acts of terrorism with caution, lest they be right. The senior GIV instructor I knew only by reputation, and he had a good one. He had been flying the GIV since day one and knew it better than just about anyone.
"Eddie," the center manager said, almost embarrassed, "I know you know the airplane backwards and forwards already but so do our instructors. You have to learn to fly it our way if you expect to pass the type check. Adam here tells me if you don't fly drift up speed they can't pass you on the ride."
I looked at Adam, who kept silent. "Tell you what," I said, "you find even one place in any Gulfstream manual that mentions the phrase 'drift up' and I will fly your speed and I'll buy you a case of wine. But if you can't, you stop teaching it and you buy me a case of wine."
"You got it!" Adam said immediately. "I'll see you after your sim."
After the sim Adam was nowhere to be found. In fact, in the next week he was a missing person. The sim instructor never again mentioned drift up and I passed my check without using it. Six months later I returned for G550 recurrent and found Adam during a lunch break.
"I know, I know," he said with a smile, "but you aren't getting any wine from me."
It was admission enough.