We agree on one thing.



No, I did not because this is not how you perform this technique. Like I said before you are arguing what you don't understand, here is what I said, "It is done by increasing the power on the downwind engine, this means in a left to right crosswind the right engine would be at a higher power setting."


We can agree here that pulling one engine will induce a drift INTO the engine with less power. Understanding this concept is important to understanding the purpose of this technique except in this scenario you are making things worse. You are inducing a drift to the right, decreasing crab which will induce more of a drift to the right, and you are applying no corrective action to change that.

Let me explain this again now that we agree on which way you will drift when one engine is reduced.

Here is the scenario, a left to right cross wind. The downwind engine will be the right engine, the upwind engine will be the left engine. Now let us analyze the goal here, we want to reduce the crab angle but we don't want to drift off centerline when we do it.

As you previously stated, reducing the power on one engine will result in a drift in the direction of the lower powered engine. We also can agree that crabbing into the wind can eliminate drift, when the right crab angle is chosen.

*Applies differential thrust technique* Since we are experiencing a drift to the right from our left to right crosswind we will be crabbed appreciably to the left to counter this. We do not like the crab angle, it seems to much so we start to increase the power on the downwind engine inducing a drift into the wind (to the left). Now that we have differential thrust giving us some drift, if we leave the crab angle the same we will drift left of centerline, so we can now reduce our crab angle.

The more you increase the power on the downwind engine, the more drift upwind you will get and the less crab angle you will need to fly the approach. Differential thrust is not used to help you go from crabbed to centerline before touchdown as has been questioned here. This action would inevitably cause you to drift even quicker off the runways. Instead, it is used to provide a drift into the wind which allows the pilot to reduce the crab angle without drifting off centerline.

See post #30 for agreement with my statements, "Yes, the downwind engine will carry more torque."

Where me and capt don't agree is I think it is better to apply this sooner instead of doing it last minute as it will give you more time to stabilize. However this is just semantics in the grand scheme of things, it is like arguing do you ender a slip just before touchdown for a crosswind or do you slip it all the way in. Well for someone who has never done it before, they won't know how much slip is needed just like you likely won't know how much differential thrust to use. So I say do it early so you can learn what you need, once you have done that then you can apply it how capt mentioned. This is just my opinion though.


Again, you don't understand and implying I am speaking out of my, well you get the idea, doesn't change the simple fact that you admittedly, as I quoted in the previous post, don't understand this.

PS If I took the "both sides of your mouth" part wrong, than my apologies and disregard these last two paragraphs.

 

"The more you increase the power on the downwind engine, the more drift upwind you will get and the less crab angle you will need to fly the approach. Differential thrust is not used to help you go from crabbed to centerline before touchdown as has been questioned here. This action would inevitably cause you to drift even quicker off the runways. Instead, it is used to provide a drift into the wind which allows the pilot to reduce the crab angle without drifting off centerline."
shdw





Ah, at last we have come to the heart of the misunderstanding.

Differential power will not cause drift upwind, it may be used to align the aircraft to the runway, but drift must be stopped with wing down into the wind, just as if you had used rudder to align. It is applied to the upwind engine, not the downwind engine. More power to the downwind engine would increase crab angle. Why not just fly a larger crab angle to get the same effect?
This is also a reason large aircraft with underwing engines can't really use this technique, they are only capable of limited wing down without a pod strike. Rudder control of alignment lets them be all they can be.

 

I agree with Jungle. You could apply wing down into the wind and apply power on the upwind engine, but you'll just have to bank more to keep from drifting downwind ... however, the nose will be more aligned with the runway.

Pushing up the power on the downwind engine, which is what shdw is suggesting, is only going to make the crab much worse.

 

Engine inoperative principles in a twin airplane

Put it in sideslip and fail the left engine, you can clearly see the upwind drift I was referring to. Assuming the left to right crosswind I spoke of before, this demonstrations shows that you will fly a less crabbed approach but your flight path will be angled into the wind due to more power on the downwind engine.

Sorry for forgetting this very important step in my previous description.

Next time one of you has some sim time give it a shot, you can argue all day I am wrong and capt was wrong, but we aren't and you will see that. This will be my last post on this topic as I feel I would have more progress explaining basic multi engine aerodynamics to a brick at this point.

Take care gentlemen I will see you on future threads.

 

Thanks for sharing that with us, looking forward to more explanations. I am sure you and your Captain will work things out to his satisfaction.

 

The reason why this isn't such a great "technique" is that you are relying on engine performance to maintain runway centerline.

You can respond faster with traditional flight control inputs rather than the spool up spool down time on an engine.

 

Mother of crap, let's just agree to disagree. I don't have an opinion on heavy aircraft doing this, but I've had to use the technique in a C310 twice, and I know I was pushing the limits. I simply pulled the left engine to idle over the numbers, left the right engine at approach power(18"/2300RPM), and wrestled her down. Obviously this is a right crosswind(BKL in the middle of winter, winds off the lake from the NW)

To solidify the many clarifications, yes I added additional airleron force to the right, due to airspeed reduction and the additional left yaw now available. Would I do it again.....probably if I was still flying boxes, and only if I was as proficient as I was when I was flying every night in the same planes.

I feel neither technique at X-winds above 25(or 30 for the heavier stuff) is probably anywhere considered smart for Pax operations. Pending your ability to get the mains down and have aligned to the runway with minimal drift is really what will make or break you, unless you have underwing engines that just got an asphault sandwich!

Good luck to all of you, just know your abilities and keep the dirty side down

 

Well at least we both agree that your technique isn't smart.

If an airplane is certified at 30+ knots of crosswind, why would it then be dangerous to have passengers on board? I can assure you, the airline isn't cancelling flights because its a little gusty and/or crosswind out there.

Heck, some of my best landings on the job were crosswind landings. One gear at a time means you can be smoooooth.

 

Never said my technique wasn't smart, in fact, I feel it was the only way to accomplish the landing in those conditions with that aircraft. I know it was pushing the limits, which could arguably be considered not smart pending on what side of the fence you were on. My side says, try it once, see if it's managable, and get the job done, if not, go-around and get the next best thing. In my 2000hrs of freight flying, I only had to divert once due to the RVR dipping just below mins(that was one of those days at 3000' you could see the tops of the towers, but not the ground)

As far as the Pax flying statement, I never used the word "Dangerous," I said "not smart." I come from the small side of aviation where we have a choice of schedule and destination. I understand fully that where you guys are going, you're going, and it's part of the job. I'm ever so conscious when training our customers and they bring someone along to show them the airplane(usually a spouse), and the weather gets a little rough etc... Hopefully that reflects where my side of the coin is being viewed from.

Curiosity peaks, what aircraft have a demonstrated/certifed Crosswind component of greater than 30kts? I seem to remember in the 727 sim while at college(guess you know where I went) that it was around 25, but honestly I forget.

Definately agree on smoother landings, many stiff legged airframes out there do much nicer jobs with a slight one-leg-down-first action

 

This thread has gotten so far off DWS1's original posting but for what it's worth, several large transport category jet aircraft are certified for maximum demonstrated crosswind landings well above 25-30 knts. There is not, nor has there ever been a "safety issue" for passengers. My first landing, during IOE, in a B-777 at ORD was with a sustained crosswind component of 31 knots. Does that make me Superman ? No way ! I'm just flying the aircraft "by the book". It's done all the time. For the record, the B-777 was certified for a maximum demonstrated crosswind of 38 knots simply because the FAA could not find a crosswind greater than that during the certification tests. The B-757 and 767 are similiar in their ability to handle crosswinds, as are a number of other jet aircraft.

Back to the original posting. A transport category turbojet aircraft or any jet aircraft is never landed with one powerplant at a reduced power setting (barring non-normal procedures)to handle a crosswind. One controls roll and yaw issues with aileron and rudder.

I'm sorry Professor...what am I missing ?????

G'Day Mates