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727 Early high sink rate crashes

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727 Early high sink rate crashes

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Old 8th Jul 2008, 01:18
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727 Early high sink rate crashes

"Almost immediately after the original 727's were delivered, there were several landing accidents resulting from an excessively high sink rate, caused by slow engine spool up times and not flying the approach by the numbers."

I've heard this information several times over the years, but searching the internet, I can't find any authoritative verification. Is it true? Can anyone point me to a writeup by a safety agency confirming it?
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Old 8th Jul 2008, 02:24
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There were four within six months. All had high sink rate, unarrested descent.

UA Lake Michigan 8/65

AA CVG 11/65

UA SLC 11/65

All Nippon - Tokyo Bay 2/66

Additionally a PA ship crashed 11/66 in E. Germany, suspected similar circumstances

Last edited by barit1; 8th Jul 2008 at 02:50.
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Old 8th Jul 2008, 03:31
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As a result of this problem, TWA blocked the Flaps 40 setting. Flaps 40 provided so much drag that a high sink rate could develop and it may be difficult to stop once it begins.

To remedy this, the Flaps 40 setting was physically blocked on all TWA 727s. Flaps 30 was the most we were authorized to use, and the most we could select due to the physical block on the flap lever. Flaps 30 does not offer nearly as much drag, making the high-sink situation less of an issue.
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Old 8th Jul 2008, 18:28
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727 Landing short

Pilot error!!!!!!!!!

Just the same, I really admired the way they took the wings apart to land a 727. There was almost nothing left when you touched down!
 
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Old 9th Jul 2008, 02:30
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To remedy this, the Flaps 40 setting was physically blocked on all TWA 727s

Each to his own ... unless the memory is failing, my recollection is that the 100 was always an absolute pussycat (ie land it like a C150) and the 200 not all that different for 30/40 other than for one's having to preprogram the mindset to the flap setting .. as I recall, other than for really gusty conditions, 40 was no great problem .. but, of course, for the 200 ... flare too high and not recognise it .. and EVERYONE on board knew all about it a few seconds later ..
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Old 10th Jul 2008, 17:18
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"This lesson (spooled-up) is still in contention with one very large operator that refuses to acknowledge nor comply with the FAA's and FSF "energy management element" of the STABILIZED APPROACH concept [they assert their own alternative standard ("at stabilized thrust") which is rejected by our industry]."
********************************************************

What do they use? Didn't some regulatory oversight agree with their procedures?

There was a learning curve going from straight wing propellor driven a/c to swept wing jet a/c. High altitude aerodynamics, high speed aerodynamics, high sink rate, slow spool issues, balanced field issues, etc, etc.
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Old 10th Jul 2008, 17:58
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There were four within six months. All had high sink rate, unarrested descent.

UA Lake Michigan 8/65

AA CVG 11/65

UA SLC 11/65

All Nippon - Tokyo Bay 2/66

Additionally a PA ship crashed 11/66 in E. Germany, suspected similar circumstances
Last edited by barit1 : 7th July 2008 at 21:50.



The UAL crash into Lake Michigan was miles (20+?) from the airport. Indication of misread altimeter, by 10,000, caused the accident. During descent accepted a descent to 6,000. Unfortunately a/c was already at 2,000, well below it's cleared altitude.

AA CVG was visual approach and they lost sight of the airport. Crashed 4 miles from the runway and is more consistent with CFIT as opposed to unstabilized final approach segment.

All Nippon Tokyo impacted 12 kms from the airport. CFIT as opposed to unstabilized final approach segment.

Pan Am East Germany crash - crashed over military training area on initial approach segment. Some suspected accidental shoot down by East Germany/Russian military. Western crash investigators weren't allowed on site. Eventually some of the parts were unexpectedly driven to the West Berlin border and handed over. (Pan Am brat in West Berlin at the time). Final cause was unknown, but it wasn't unstabilized final approach segment crash.

grumpyoldgeek - in my opinion (IMO), except for the UA SLC crash, these accidents don't qualify.

You can search www.airdisaster.com, or other crash investigative websites, and enter B-727 in the databases. There might be others that IMO would qualify. I'd also check out B-707, DC-8, DC-9 and B-737 crashes in the 1960-1970's. They might have had some unstabilized final approach segment crashes that are, over time, getting lumped together.
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Old 10th Jul 2008, 18:13
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Barit1,

Just reread my post. We could get into a circular argument about high sink rate, unarrested descent vs. CFIT crashes. Almost every accident is by definition "unarrested descent".

IMO the AA CVG crash is an example. Crew took a visual approach, ceiling reported at 1500 BKN. While trying to tune ILS frequency and get established on ILS they flew into the ground. Unstable approach? Blame it on high sink rate/unarrested descent? Or perhaps basic loss of situation awareness and basic instrument crosschecking?

Me? I'd blame it on loss of SA and basic flying. The NTSB makes no mention of high sink rate/spool issues.

NTSB? PROBABLE CAUSE(S)
PILOT-PLTS DID NOT MONITOR ALTIMETERS DURNG APPRCH
WEATHER - RAIN
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Old 10th Jul 2008, 18:18
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grumpyoldgeek,

After rereading you post I realized I focused on the high sink rate and unspooled portion of your post. Had I focused on the "not flying the approach by the numbers" I would agree that all of these crashes can be attributed to that probable cause.

That's almost a Catch-22 - did poor flying cause the crash? Yes. IMO only one is directly attributed to high sink rate problems(SLC), AA CVG might have been except they crashed 4 miles from the airport as opposed to less than 1-2 miles from the field.
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Old 10th Jul 2008, 19:53
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IMHO

It's been almost 25 years since I flew both the 727-100 and 727-200, but as I recall, the SOP for that aircraft at my company required being stabilized on the approach no later than 1500 feet AGL (as opposed to 1000 feet AGL for the other aircraft in our fleet). This was due to the aircraft's ability to develop high sink rates with a dirty configuration, relatively low airpseed, and unspolled thrust conditions.

While I haven't that much time in the 727 (maybe only 2800 hours total time), I recall that, in order to get a good landing, the flare technique was somewhat different from other aircraft I flew. As I recall, as you came across the fence, you eased back on the yoke slightly...as doing so, increasing thrust slightly. Then, as nearing the runway, we relaxed the back pressure...perhaps even pushing a bit on the yoke...and perhaps increasing just a bit more thrust. Such techinque resulted on rolling it on at Vref +5 to Vref +10 or so.

Again, as I recall, the airplane stopped well...so much so that the nose wheel brakes were removed by most carriers....not necessary. Between the big main wheels and brake assemblies, and the reverse of those three engines, stopping usually wasn't a problem.

Overall, the airplane flew like a dream. I loved it. But, you had to be careful not to scrape the tail skid...especially an issue on the -200 model. Thus, on takeoff, we normally did the 'two-step' rotation technique. I can't recall, specifically, the numbers...but I'm thinking the -200 hit the tail skid (struts compressed) at 10.5 degrees nose up...11.25 degrees nose up on the -100...so, we did the first step rotation to about 9.5 degrees, until she lifted off, then, further rotated to an initial target pitch of 15 degrees (+/- for the various factors).

Sorry if my memory is failing...which is proved daily...so, someone please correct me.

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Old 10th Jul 2008, 20:48
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Sorry if my memory is failing...which is proved daily...so, someone please correct me.
No, that's pretty accurate. I ended up with about 7,000 hours in the 727, mostly in the 100. I my experience as well I found the 100 much easier to land smoothly than the 200. If fact it is astonishing how fast you can stop a 727 on landing.

Now, in regards to the flaps 40 landings. We were cautioned about the high sink rate that you get into with 40 flaps, however, we were told that reason that most airlines had blocked out the 40 position was two fold. First was for fuel savings, it takes a lot more power at flaps 40 verus 30 on final and secondly for noise abatement. We had flaps 40 available on our 100s and 200, we seldom used that position for the above reasons. When the aircraft were modified for stage III the 40 position were blocked. However, we could remove the block if we deemed it necessary for operational reasons.

One thing I can tell about landing with flaps 40, when you pull the power off, you land, right then. I never dumped the 02 masks, but I've been on board when other pilots did. In fact one memorable landing a guy not only dumped the masks, but the life rafts as well. And that was a flaps 30 landing.
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Old 10th Jul 2008, 21:10
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I got the privilege of flying the 727-100, the -200 with the -7, -9 and -15 engines along with two re-engined 727s with the JT8D-200 series engines. It was not a difficult machine to fly but it did require planning.

The initial flaps dribbled out very slowly but it was possible to go to flaps 25 without the gear horn that could NOT be silenced. Flaps 30 or 40 and you had the horn. Drag increased considerably beyond flaps 15 but it was possible to leave thrust at around 2700-3000lbs/eng and configure to the next flap setting as the drag increased. And you could actually go down AND slow down in the 727, something not available in the 737 or the 757/767.

At flaps 30 the machine was very stable BUT if you had a speed decrease, it was necessary to keep adding power until the speed decay was arrested and then start bringing power back off. You could NOT add a bit of power.. add a bit of power and arrest the speed decay. You had to be aggressive.

Flaps 40 increased drag considerably but not unduly. I had flown the KC-135 and we used flaps 50 so maybe I was conditioned. Some fellow aviators never used 40 but if you added about 4-500lbs/hr/eng, things worked out nicely, especially on wet or contaminated runways. We used to call flaps 40 "give me 50 percent wing disassembly'. Our flaps 40 position was never locked out although I believe after the merger that did occur. (I got bumped during the merger).

You could definitely develop a high sink rate in the 'seven two' but you could also do that in the early Lear 20 series.

As for landing, there were multiple techniques. For me, it was reduce power and hold the nose exactly where it was. Others used a BIG flare and many of the BI guys had perfected the 'shove' where they released a bit of back pressure after the slight flare and that cushioned the landing.

I never got the 'rubber jungle' in a landing but had a few friends that did. You could definitely rattle some teeth with a firm landing.

The Mighty Tri-Motor is one of the grandest flying machines ever built IMHO. I enjoyed my time on it although I could never figure out the slightly off center yoke in the -100. I enjoyed the 727 much more than my time on the 737.
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Old 10th Jul 2008, 21:43
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That slight pole forward before a skating on greaser was something I saw many times watching from the holding point. Arsey and classy it looked.

Straight after the early prangs in the states a movie was made about the techniques for a safe, stabilised approach, widely distributed to 727 operators.

Rather sorry never to have made it onto the three holer. She of the ventral entry. First encounter was at Mascot in '62 when the demonstrator came in on it's world tour. Plastered with all the logo stickers of all the airlines that had ordered them. Sales staff handing out all the pins and ties and little diecasts you asked for. And just about any odd or sod could cadge a ride.
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Old 10th Jul 2008, 21:54
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Unrelated Question...Forgive Me

Wileydog3....

Did you fly the early KC-135 with the old engines that had water on takeoff? How much thrust did those engines have...both with and without
water?

It's my understanding that the max takeoff weight for the 135 (under war time conditions) was 300,000 lbs. Is that correct?

Just want to calculate the thrust to weight is with one engine inopt. I heard the plane, at 300,000 lbs, didn't fly too well with one engine inopt.

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Old 10th Jul 2008, 22:11
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There was also this accident, involving B727-112C YA-FAR of Ariana Afghan Airlines on approach to runway 27 (as it was then) at London (Gatwick) on 5 January 1969.

Although never having flown the 727, I have to say that I have always understood it to be "potentially unstable in the landing configuration".


JD

Last edited by Jumbo Driver; 10th Jul 2008 at 22:31.
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Old 10th Jul 2008, 22:44
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Thanks for all the great info. This is stuff that isn't available anywhere else in the world. Shades of Earnest Gann's writing here.

Thus, on takeoff, we normally did the 'two-step' rotation technique. I can't recall, specifically, the numbers...but I'm thinking the -200 hit the tail skid (struts compressed) at 10.5 degrees nose up...11.25 degrees nose up on the -100...so, we did the first step rotation to about 9.5 degrees, until she lifted off, then, further rotated to an initial target pitch of 15 degrees (+/- for the various factors).
I remember those two step rotations as PAX, flying out of SEA and PDX. The second rotation felt more like 45 degrees in the back.
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Old 10th Jul 2008, 23:01
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ILG,

You stated that TWA's blocking the Flaps 40 was for an unrelated reason, but I can tell you that while in 727 class at TWA we were told specifically that the Flaps 40 setting was blocked as a direct result of the SLC accident, related to excess drag at flaps 40. Had they been at Flaps 30, the sink rate could have been arrested and there would not have been a problem.
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Old 10th Jul 2008, 23:29
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You stated that TWA's blocking the Flaps 40 was for an unrelated reason, but I can tell you that while in 727 class at TWA we were told specifically that the Flaps 40 setting was blocked as a direct result of the SLC accident, related to excess drag at flaps 40. Had they been at Flaps 30, the sink rate could have been arrested and there would not have been a problem.
Sorry, I should have included in my post that in my training, Dalfort ie. Braniff, that we were told that some airlines did block out the 40 position for the sink rate issue as well for fuel and noise.

If I recall correctly with flaps 40 you needed around 5,000 fuel flow but only 3,000 with 30 on final. For minor power adjustments I just used #2 and left 1 and 3 at a constant setting.

One of the things I loved to do in the 727, when able, was to close the throttles at 10,000 feet and not touch them again until flaps 30 and gear down. Usually could not do that because of ATC and/or traffic.
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Old 11th Jul 2008, 03:08
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T-tail

The problem with the 727 that was not understood initially was the deep stall.

The T design of the horizontal stabilizer elevator allowed the wing to blank the tail when the airplane was allowed to get too slow in a nose high attitude.

The drag of 40 degrees of flap could slow a 727 pretty rapidly unless a lot of power was added at the same time as the flaps were lowered.

The airflow to the aft mounted engines was also disrupted. With the elevator or even a stabilator in this condition (nose high and slow) and no air getting to the engines, the aircraft was uncontrollable. It was stuck in a stalled or near stalled condition.

This was new territory in this second generation jet, and several were lost before the problem was figured out. Flap limits and higher minimum airspeeds took care of the problems, and as long as the new limitations were adhered to, the aircraft was safe.

As for the difference in landing performance between the -100 and the -200, it had to do with main gear position in relation to the CG. when flaring the longer -200, the main gear could be slammed into the runway as the nose came up. Hence the slight pitchdown or relaxation of back pressure on the control wheel just before touchdown that savvy pilots learned.

We don't see designers opting for T tails these days.
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Old 11th Jul 2008, 04:28
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back on the yoke slightly...as doing so, increasing thrust slightly
I never flew the 727 but have fair amount on the various 737. Interesting about your point above of increasing the thrust slightly during the flare.

I have seen this technique used in the 737 and also in the simulator. When asked the pilots concerned their technical reason for giving a "burst" of throttle at the flare, people couldn't explain why - although I realised after watching many of these power bursts it was often a reflex action - despite their aircraft was perfectly positioned in the flare for a good landing. In other words it seemed a good idea at the time!

In the simulator I found it difficult to convince some 737 pilots that there was simply no point in this burst of thrust as all it did was cause the aircraft to sometimes balloon slightly and land deeper into the runway. In some pilots this habit was so ingrained one could not break it rather like the jerk that occurs involuntarily when you hit your knee lightly.
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