Thursday, November 02, 2006

Gratuitous airplane pic!

Today was a New York trip - the weather was perfect except for a 120 knot wind which caused a few bumps in both directions. When we landed back in Toronto, it started to snow and by the time I made it home from the airport, there was a mini-blizzard going on. It's cleared now, but I was happy and sad that I have seen the first of this year's snow.

In other news:

I have been jogging every day and so far I have lost a pound. Hey, it's a start. I tell you though, it nearly killed me to go for breakfast in New York today and have a fruit salad with unbuttered toast and a mug of green tea. But it's worth it if I get to dress in a bear suit for my wedding.

Now to the point of today's post:

I did the return leg to Toronto this afternoon, and as we came in to land it was really windy and gusty. In fact, we got a taste of windshear - nothing too skeery, we just lost about 15 knots of airspeed on short final approach but I had already added 10 knots onto our normal approach speed due to the gusty winds, so it wasn't a huge deal and we weren't even close to stalling the plane or anything. As I watched the speed drop, I pushed the throttles forward in order to get more power from the engines, and after a couple of seconds they spooled up and gave me an extra boost, so I was able to make up the 10 knots of speed I lost in very short order. And I must say I had a sweet landing, even though it was in a 60 degree cross-wind of 12 knots, gusting to 28 knots. Hey, I get lucky once in a while :)

It was interesting though; in a piston engine or in a turboprop like the MU-2 (not in all turboprops though), the pilot has nearly instant access to engine power. If they need it, they just push the throttles forward and the engines will respond immediately.

In a jet, there is a bit of lag between the time you ask the engines for power and the time they actually deliver it - in our plane it seems to be a couple of seconds or so, and I have to take that into account when planning a difficult arrival. The lag is a result of the engines having to speed up considerably. In the MU-2 turboprop I flew, the engines essentially ran flat-out all the time, so power was constantly being generated, but in my jet, when I am close to landing, I will typically use a power setting of only 60% of the maximum engine speed. In a piston engine it's only a matter of a thousand rpm or so between a low power setting and a high power setting, but in a jet it's a matter of going from 20,000 rpm to 35,000 rpm and it just takes longer to do that.

End result: I have to anticipate some problems before they occur and be ready to deal with them very quickly, otherwise I could find myself needing power from the engines sooner than they are able to deliver it.

So I guess I have to pay attention.

And that's what I thought about today :)


Garrett said...

The relevant FAR in the US allows for 8 seconds between flight idle and go around power. It doesn't actually say that the engine has to hit max power in 8 seconds, just that the manufacturer can't take credit for power levels beyond 8 seconds in required performance.

Its a really interesting topic because people talk about the whole pitch/power/speed approach relationship thing and it seems that the time variable for power adjustments has to be a part of those tactics.

With respect to piston engines, you are right that the delay is practically nonexistent. I datalogged a 2 stroke engine that could could accelerate at 20,000rpm per second. For an EFI engine at a given speed to go from no load to full power output takes only a couple revolutions of the crank. Probably a few more for most conti/lycosauruses, but very little time in any case.

There is a FAR that says that unless you have a good reason not to, you should always use the cleanest possible flap setting for the conditions. I wonder if in a big windshear event it is better to be in a draggy approach with the turbines spooled up, or in a cleaner config with a higher approach speed but more time to get power put in. I guess the stall margin is numerically larger at the higher vref, and that is probably the most important factor.

david said...

Jogging's great, but it doesn't burn many calories. You can supplement by moving around as much as possible in your ordinary life: ALWAYS pick the furthest possible parking spot at work, the mall, etc. (or even better, walk there); volunteer for every errand to walk out and get bread or milk or to mail some letters; park your jet on the far-away apron that nobody uses, and have it towed in for startup when your passengers come; etc. etc.

It might be worth investing in a cheap pedometer, and trying to make 10-15K steps/day, including your jogs. We really want to see the wedding pictures with the bear suit.

Anonymous said...

another winning approach to the calories in- calories out margin is to follow a simple, healthy diet that offers lots of veggies , raw or cooked and protein the size of a deck of cards three times a day and low carbs( anything that is white: pasta, spuds, rice, flour sugar etc). No soft drinks, booze or candy.You can get a lot of filling- feeling with the veggies and the weight will drop off. Bonus is the amazing energy that these food choices give. I've already picked out the furry critter costume I will be sporting. So move da body and hold off on the high calorie foods..We're rooting for the Bear!!