[Question] Controlling 737-800 with one engine

[TChapman500 0]

I have an interesting situation. My landing gear has failed to retract, forcing me to turn back to the airport, then just as I'm getting ready to make a left-hand, 180-degree turn to align with the runway, the left engine fails. Now I need to make the turn while compensating for the loss of the engine, and I only have 2,000 feet to play with. I tried, but the aircraft stalled and crashed.

 

Is a 200+ foot-per-second straight down decent with a full tank of fuel survivable?

[Chock 17,769]

Well, the problem should not actually have occurred if you were following the correct procedure. Which would be to climb to a hold position given to you by ATC, and then orbit until you had burned off enough fuel for a safe landing, because the 737 has no fuel dumping capability.

 

Because it does not have the ability to dump fuel, the 737-800 was required by law to be able to climb at a incline of at least 2.4 degrees with one engine failed when at MTOW (although how easily it does that depends on when the engine fails, if it is well after V2, then it will accelerate very well). The 737-800 would not have received certification if it had been unable to do all that, since an engine failure, whilst rare, is not unknown.

 

All airliners in the 737's class have to be able to withstand a 600 feet per minute descent rate touchdown at normal landing weights (which would be uncomfortable for passengers, since it would probably exert 2G on them), and a 370 feet per minute descent rate touchdown at MTOW, which might damage something but would not destroy the aircraft.

 

At MTOW, you are roughly 30,000lbs over the minimum landing weight, but even with the additional drag of the gear, a 737-800 would still be able to climb, since the gear can in fact withstand speeds of 270 knots (.82 Mach) and doesn't really add a massive amount of drag, the gear will slow things down of course, but it is the flaps at full deployment which add most of the drag on a descent.

 

No pilot in their right mind would immediately turn back toward the airfield at MTOW on one engine with the gear down at only 2,000 feet AGL when they knew that they could climb, burn off fuel, and then make a safe approach.

 

Turning back to the airfield at low speeds after some kind of failure on take off is a notorious pilot killer and generally speaking, it is a 'big no no' unless you have absolutely no other choice and really know what you are doing. Even some famous flying aces have been killed trying to do that, among them, James McCudden, who was in fact also an instructor and known to be an excellent pilot. I have done that once in real life, but that was in a two seater glider after a cable break at about 600 feet AGL, and to get away with doing it, I dived to 300 feet whilst doing a dogleg left, in order to get some speed on the clock and room to turn, then did a very carefully coordinated and swift 60-plus degree banked 180 degree turn and landed back downwind on the large grass airfield I had just taken off from. Apparently, my wingtips cleared some trees by less that 100 feet according to a guy in the back yard of a local pub who saw it happen, and he said it looked (and sounded) very cool LOL. But you simply could not do that sort of thing in a powered aircraft - they don't have the necessary glide ratio, my glider had a 38:1 ratio, an airliner typically has a 4:1 ratio - and especially not an airliner at MTOW, so it would be insane to try it. You never turn back to the airfield after an engine failure at low altitude; you always land ahead, or you will die.

 

So yes, on a decent runway, a 200 fpm touchdown at MTOW in a 737-800 would be okay, but what would not be okay, is the 'friendly' discussion you would be having with the chief line pilot for having done such a thing in the first place!

 

In short, don't turn until you have some speed on the clock, get some altitude, get the thing in a stable hold, and then either try to solve the problem by doing a relight and trying to get the gear up, or if you can't get it sorted out, burn off fuel and then land when you are at less than 145,000lbs total weight.

 

Al

[TheBFG 1]

Chock's reply contains just about anything you need.

 

I'll weigh in with one simple tip: When an engine fails and you don't do your thing with the rudder immediately, you're not going to make it. Also if autorudder is on, get rid of it as soon as you have asymmetrical thrust. It sounds like you got into trouble soon after takeoff. When an engine fails, don't turn. You also never make a 180 to land downwind in ANY aircraft.

[TChapman500 0]

Um, the descent rate was 200 feet per second judging by how much the altimeter was changing by during the fall. That's 12,000 feet per minute (on impact). What does MTOW mean?

 

The gear failed on take-off, so I immediately canceled IFR and turned left 180 degrees to land back on the runway. It's after that first turn that I had the engine failure. I was trying to maintain 200 kts because I didn't know how much the gear could take (I know now, thanks). I had to go from 3,000 to 2,000 because I was well above the glide slope (after the decent, which was a little after I had made that first 180, is when the engine failed). 2,000 put me below the glide slope, which is where ATC would have put me until the aircraft intercepted the glide slope (which I would have to turn around in order to do that).

 

I think it was about 5 seconds after the engine failed that I realized it. And it was because the heading indicator was telling me that the plane was turning, even though the wings were level. That's when I went full throttle on the remaining engine and full right rudder (I released some rudder input to try to turn to line up with the runway).

 

So, I should not go full right rudder when the engine fails? And how long will the 737's fuel last?

[TheBFG 1]

Not to be a party pooper, but I'd suggest you do some reading on the basics of operating a basic aircraft before diving in with a 737. There's a whole lot of stuff you need to get right in a Cessna 172 first if you want to fly a 737 properly. For example, asking how long the fuel in a 737 will last or what MTOW means... it will be very difficult for us to answer your questions if you don't know these basics. Do some reading and have fun with it! Handling asymmetric thrust is not something any real pilot learns before he knows just about everything there is to know about flying singles.

[Chock 17,769]

MTOW is maximum take off weight, i.e. that would be as heavy as you can possibly be and still be okay to lift off.

 

My mistake, 200 feet per second, is roughly 136 miles per hour, so if you hit the deck doing that speed vertically, yes, you probably would die, in fact there would probably be very little left of the aircraft or the passengers to srape up by the time they'd put the fire out. As a comparison, the F-4 Phantom was designed for carrier landings, which are often described as a 'controlled crash', and so its landing gear was designed to withstand a 23 feet per second descent rate, so you're coming in at nearly nine times the descent rate a carrier-based fighter is designed to withstand, which isn't going to end well at all.

 

Al

[TheBFG 1]

And remember that MTOW is only valid at sea level and 15 degrees celcius or below... otherwise it decreases! I remember not being able to figure out why my 747 couldn't climb out of Johannesburg (5558 feet elevation) on 3 engines at max weight. Turns out I was a good 100 000 pounds too heavy!

[drnex 1]

And remember that MTOW is only valid at sea level and 15 degrees celcius or below... otherwise it decreases! I remember not being able to figure out why my 747 couldn't climb out of Johannesburg (5558 feet elevation) on 3 engines at max weight. Turns out I was a good 100 000 pounds too heavy!

 

Huh?? This is so wrong.

 

MTOW is the heaviest weight at which the aircraft has been shown to meet all the airworthiness requirements applicable to it. MTOW of an aircraft is fixed, and does not vary with altitude or air temperature or the length of the runway to be used for takeoff or landing.

 

What varies with Density Altitude (ie pressure altitude and temperature) is your takeoff and landing roll required.

 

A different weight the "maximum permissible takeoff weight", or "regulated takeoff weight", varies according to flap setting, altitude, air temperature, length of runway and other factors. It is different from one takeoff to the next, but can never be higher than the MTOW.

 

[TheBFG 1]

Huh?? This is so wrong.

 

MTOW is the heaviest weight at which the aircraft has been shown to meet all the airworthiness requirements applicable to it. MTOW of an aircraft is fixed, and does not vary with altitude or air temperature or the length of the runway to be used for takeoff or landing.

 

What varies with Density Altitude (ie pressure altitude and temperature) is your takeoff and landing roll required.

 

A different weight the "maximum permissible takeoff weight", or "regulated takeoff weight", varies according to flap setting, altitude, air temperature, length of runway and other factors. It is different from one takeoff to the next, but can never be higher than the MTOW.

 

Dude, I'm just trying it explain it in an easy way for the OP :)

[TChapman500 0]

What does OP mean?

[Ponk 51]

PMDG, the new search engine!

[TChapman500 0]

What does PMDG mean?