727 Handling Characteristics

[xxmikexx]

In order to avoid hijacking the When Did You Start Simming thread, I here respond to angles355's comparison of a 727 to a Corvette with respect to its handling characteristics ...

skylab, I will defer to anything you say regarding correcting errors in this post. You have flown real 727s, I have not.



angels355,

727s were not Corvettes, they were motor homes. They were slow to respond even with hydraulically boosted controls, and for low speed roll control they had to use spoilerons to compensate for the limited aileron control authority.

They had such low total drag that at altitude it took them about 20 nm to slow from .81M to .60M, a good 5 nm longer than most transport aircraft require, and frequent use of spoilers during descent was required to keep the airspeed in the vicinity .60M.

Finally, unless a 727 approach was flown with respect it was very easy to get on the back side of the power curve, a condition impossible to recover from while at low altitudes on the glide path.

This is one aircraft the pilot had to stay way ahead of, unlike a friend's full race '64 Corvette, which responded instantly and precisely to my every input, including steering by throttle through tight curves.

[Kimber]

This is a bit OT, but about a 727 and it handling!!

A 727 needs 5000' and the runway at Springdale is 5300'!!

http://www.lubbockonline.com/news/032997/razorbac.htm

If this is OT too much, please feel free to delete!!

OK??

[xxmikexx]

Kimber,

As far as I'm concerned your story is very much on topic. I'll add to it the fact that in the days when Aspen CO was a 3500 foot gravel strip, some clown put a corporate 727-100 in there and got it down and stopped, just to prove it could be done.

However, as I recall the aircraft had to be dismantled on site and the large pieces trucked out to Flatland. (Can you say "career over"?)

[angels355]

"Finally, unless a 727 approach was flown with respect it was very easy to get on the back side of the power curve, a condition impossible to recover from while at low altitudes on the glide path."

When descending in a 727 there are two serious problems you have to worry about, I've mentioned before the aerodynamic shadow the nose of the plane casts on the middle engine, so you have to be prepared for lack of power when pulling out of the descent.

Also, exactly what you're saying about staying staying ahead of the plane's power curve, when descending in a 727, before leveling out you need to advance the throttles way ahead of time in order to spool them up way in advance of leveling out from the descent, otherwise you'll still be spooling up as you splat on the ground.

I'm fairly certain however that they had a lot of power, and pilots loved them. I was looking at a short 727 perhaps a year ago and I was amazed at how small it is, reminded me of a large business jet.

While there were difficulties in flying the 727, there were also incredible performance aspects too, like for example if you're at fairly high altitude, if you can see the runway below, you can descend so steeply that you can land on that runway due to all the slats, flaps, and spoilers. In that respect it flies very hot/high performance, plus also I think it had a lot of power.

The 757 however has incredible power, it's jaw dropping. The 727 used to be one of the hottest planes to fly, and I've thought that the 757 is now the 727's logical replacement in that respect.

Info from a real 767/757/727 pilot, also flew for a short while "speed bumps" (737's, too slow, so were in the way, therefore "speed bumps")

http://www1.dfrc.nasa.gov/gallery/Ph...m/ECN-3831.jpg

[skylab]

skylab, I will defer to anything you say regarding correcting errors in this post. You have flown real 727s, I have not.

Not true. Flew the 7-THIRTY-7, not the 7-TWENTY-7. Never liked it; had the engines in the wrong place!!

[angels355]

Mike,

Spoke to the 727 pilot, he says that regarding the roll rate that it was not deficient at all. In all respects it was a beautiful plane to fly. You have to fly it according to the manual, and not go outside the flight envelop, however in every respect it was a delightful beautiful plane to fly. He mentioned that the 727-100 was a little weak in power, but on the others there were many power configurations that were very satisfactory. He was the one who told me about the aerodynamic shadow and spooling up the engines before leveling off from a descent, but he told me that those were very minimal concerns, you just spool up the engines before leveling off and it's no big deal, and the loss of power due to the aerodynamic shadow was not that great, it was there but not that great. He said that when you're descending that you have plenty of speed, then before leveling out you spool up the engines, and by the time you reach the outer marker your gears are down and you've got full flaps, and the engines are spooled up and you've got power, it's a power-on type of landing. When you land, and have to do a touch and go or do a go around missed approach, your power is already up and you can easily take off or go around as the power is already up. You just don't get fancy and fly outside the envelop. When flying passengers you always bank gently so you never fly like a hotrod, but if you're empty or flying cargo then you can do some more aggressive banking and flying. But he says that the roll rate was not deficient at all. Spoilers used to assist the ailerons and roll rate are common in airliners. From my own studies the 747 uses three control surfaces to assist in the roll rate, inner and outer ailerons (turn off at a specific speed), and spoilerons. I'm guessing that modern airliners might also use the horizontal stabilizers through fly by wire control to also assist in the roll rate, at least that's what happens in fighters so I image the technology is available for modern airliners also. The roll rate was also assisted by the engines being close to the centerline, like an ice skater, with arms extended the spin is slow, with arms retraced the spin is fast.

Because the engines were very close to the centerline, an engine out situation was very easy to control, there was very little difference in yaw for example with an engine out, unlike the #1 or 4 engine out on a four engine plane like a 747 or dc8. The really big difference between the engines from then and now, the 727 had very low bypass ratio engines which are excellent at high altitude, but not as terrific at low altitude and most importantly to airliners have much less fuel efficiency than a very high bypass ratio engine like you see on a 757. A high bypass engine also serves as an aerodynamic muffler, the cool air from the bypass fan blades surround the hot air coming out of the center of the engine, this greatly reduces sound levels. On a zero bypass ratio engine like you'd see in a Lear 21, all you've got are the hot ripping high speed gases coming out of the engine with no shielding of cool air around it, so it is so loud that it is banned from certain types of airports. High bypass engines are more similar to turboprop engines, they respond much more quickly at low altitude like a turboprop would, definitely not nearly as fast as a turboprop however much more similar to a turboprop than a zero bypass engine which only relies on centerline hot jet gases coming out of the jet engine, instead of additional thrust from the large fan blades that provide prop type of thrust. That is why spooling up the 727 engines well in advance, and doing a power on landing is important, as just like you were saying that there's no instant acceleration like a turboprop or corvette, you have to spool up the engines well in advance. Other than that however, it's my opinion that otherwise the 727 was the hotrod of its' day and pilots loved them for that.

For the most part, I believe pilots loved the 727. And it was a very high performing plane, with full flaps and gears starting at a relatively high altitude if you could see the runway down below, it's highly likely that you could descend fast and land no problem. It was a great plane, but now the 757 is the new hotrod, it has unbelievable engine and thrust to weight performance.

[xxmikexx]

angels355,

I didn’t say that the 727 was deficient in roll rate, I said that it took the addition of the spoilerons mechanical logic to make the roll rate acceptable at low airspeeds. And I didn’t say that it wasn’t a beautiful plane to fly, I said that it wasn’t a Corvette. And yes, it was underpowered. It took forever to reach, say, FL320.

And yes, I too love the aircraft. It is all that I fly - - 727-200. I loved it as a passenger and I love it today as an occupant of the simulated left seat ...

But "handles like a fighter"? That was a promotional remark made by a Boeing test pilot. What did you expect him to say? "Handles like a motor home?"

Any average pilot could fly a 727 well, he/she just needs to be aware of the aircraft's performance envelope. Get outside it on approach - - get behind the power curve -- and you will do what so many 727s did -- crash.

[skylab]

Get outside it on approach - - get behind the power curve -- and you will do what so many 727s did -- crash.

Ahh.....I would like to see a list of "so many" accidents where the "cause" was listed as you stated.

[xxmikexx]

skylab,

Salt Lake City
JFK
<somewhere in Florida, I'll have to look it up>
.
.
.

There are more, I'll find them and make another post in this thread late this evening.

[SLuggy]

If I may be so bold, I'd guess that the ratio of airframes lost to airframes built would be very much in favour of the 727 compared to the 737.

A few 727s were lost upon introduction to service in the early 60s, but remember that the average short/medium haul pilot in those days were used to piston engine planes, and most wouldn't have flown turboprops or even DC-6/7 and Connies. Once pilots knew how to fly a jet transport, the rate of accidents dropped quite significantly.

Plus the 727 still looks great!

Cheers, SLuggy