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I've never seen a 727's aft stairs open, but presumably, based on an Wikipedia image and common sense, they do reach the ground when the aircraft is on the ground. Furthermore, (as I understand it), airliners land with a positive pitch, which means that assuming a level runway, the rear of the aircraft will touch down first. However, this suggests that if the aft stairs of the 727 were open during landing, they would impact the ground during landing and, given the pitch, do more than scrape the ground and cause damage to the aircraft.

However, DB Cooper's jump left the aft stairs open, and (as far as I can tell) it seems that the landing was uneventful besides the stress of having a hijacker potentially on board (although it's quite understandable if no one made any record of it, given there were slightly more important things to deal with).

If DB Cooper's flight did land without damage, why is that—did the 727's aft stairs not fully touch the ground? If the stairs did impact the ground, was there sufficient damage to require repairs?

(I meant this question to be more about the 727 than DB Cooper, but since his was the only landing with stairs open, there wasn't much room for speaking in general terms).

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I do not think they landed with the airstairs down: The airstairs are powered to get them back up since they are heavy, and this feature can be operated from inside the aircraft as well.

The following answer is of Yahoo answers and while I can't confirm is accuracy, it sounds very plausible:

There are 2 control handles for the airstairs on a B727, one under a panel on the lower fuselage right beside the stair forward hinge point, and one at the top of the stairs behind a panel on the left side which can only be accessed when the rear cabin door is open. Because the cabin door can only be opened when the aircraft is unpressurized, this usually would prevent its actuation in flight. However, after the D B Cooper hijacking a device was added referred to as an anti-hijack vane that would swing over when the aircraft was in flight and prevent the door opening. To close the door either an electric hydraulic pump has to be turned on in the cockpit, or a hand pump beside the lower control operated while either handle is held to the close position. The door will free fall open without hydraulic pressure, but the support arms may have to be pushed to an overcenter position.


Assuming that the air stairs were deployed, it may be that the force of the airflow passing by would have been sufficient to spare the stairs from a tailstrike. The stairs have a large surface area and moving at perhaps around 100 knots when the nosewheel touches down would still generate a considerable force to push them into the fuselage.

The term deployed may also suggest that the airstairs may have been damaged and uable to retract the whole way, leaving it halfway stuck but still out of tailstrike range.

The aircraft was empty at the time which would have helped in either situation.

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The aft airstair was partially deployed for the duration of the approach and landing.

The transcripts of ATC communications between NW305 and various ground stations are freely available (and a fascinating read). The relevant communications (with Reno) begin on PDF page 87 (numbered 213). Below are the mentions of the airstairs from that point on, with times given in PST, 1971-11-24. I added the text in brackets for clarity.

22:35, NW305: OKAY AH WE'RE TRYING TO MAKE CONTACT WITH [Cooper in] THE BACK [of the airplane] NOW AND AH WE'RE GOING TO GET THESE STEPS UP BEFORE WE CAN MAKE OUR LANDING...

22:43, RENO: NORTHWEST THREE ZERO FIVE WHAT'S THE STATUS ON THE STAIRS NOW SIR

22:43, NW305: AH WE HAVEN'T BEEN ABLE TO GET AHOLD OF ANYBODY [in the back of the plane] YET UH TRYING TO CONTACT HIM AND THEY'RE STILL DOWN SO I WE HAVEN'T DECIDED YET AH WE MIGHT COME IN AND LAND WITH THEM DOWN THERE'D BE SOME SPARKS SO

22:48, NW305: APPROACH AH THREE ZERO FIVE WE CAN'T SEEM TO RAISE HIM BACK THERE WE KIND OF HATE TO WE'D JUST AS SOON LAND WITH THE THING HANGING DOWN IT ISN'T ALL THE WAY DOWN AND THEN PROBABLY WON'T HAVE ANY PRESSURE ON IT SO WE HOPE IT'LL (unintelligible) FREE...

22:57, NW305: ...WE'RE NOW MARKER INBOUND AND UH AH WE'RE GOING TO BE LANDING WITH THE AIR STAIR IN THE DOWN POSITION AH WE DON'T SEEM TO GET ANY RESPONSE FROM OUR FRIEND IN THE BACK

[The aircraft touches down and is taxiing.]

23:03, NW305: SEE ANY SPARKS COMING OFF THE TAIL AT ANY TIME ON AH TOUCHDOWN

23:03, RENO: NEGATIVE NONE AT ALL THE ONLY THING THAT'S VISIBLE ON THE TAIL IS LIGHT AH APPARENTLY ON YOUR RAMP

23:03, NW305: ROGER UNDERSTAND STAIR LAMPS AH STAIR LIGHTS

23:03, RENO: I DO SEE SOME AH SPARKS NOW JUST A FEW AH TRAILING YOU AH AS YOU'RE TAXIING IN

23:03, NW305: OUR AH PASSENGER TRIED TO DISEMBARK

23:03, RENO: I STILL DON'T AH GETTING A FEW SPARKS NOT VERY MANY AT ALL

23:03, NW305: OKAY WE'LL TRY TO SLOW OUR TAXIING HERE AS MUCH AH IT PROBABLY IS DRAGGIN AH

Why did the crew not retract the airstair before landing?

The airstair can only be operated from two positions: one in the main cabin and one on the exterior of the aircraft. It cannot be operated from the flight deck. The testimony of Tina Mucklow, the flight attendant whom Cooper interacted with almost exclusively, reveals that

Approximately four minutes after takeoff, [Cooper] stood up, told [Mucklow] to go to the cockpit and close the first-class curtains, and for no one to come out from behind the curtains.

It should be noted that the airstair was still closed and locked at this point. In fact, it was Cooper himself who performed the deployment:

...he asked her to demonstrate to him the procedure for opening the rear door and extending the stairway. She did this and was under the impression that he understood how to do it. She commented that it occured to her at this time that this was the only function of the aircraft which she had discussed with the hijacker during the time she had been with him which he did not seem to be fully aware of.

Even though before Mucklow left Cooper in the cabin "...she pleaded with him to take the bomb with him and he said he would take it with him or disarm it...", nobody could be sure, so complying with his demand for no one to enter the cabin was the obvious choice. Even after the crew suspected he had jumped, there was still some chance that he was present. That—on top of the clearly dangerous situation of being unrestrained in an airborne jet transport with a door open—compelled the crew to sit tight in the cockpit and land with whatever configuration they could control from there. Indeed, third officer and right-seater on the flight Bill Rataczak stated that

...no member of the crew departed from the cockpit to check on the presence of the hijacker following the arrival in the compartment of hostess Mucklow, who had locked the door behind her.

How did the airstair remain partially deployed on its own?

The airstair is in contact with the tarmac when deployed on the ground. In fact, it's designed to essentially wedge itself against the ground and act as a tail stanchion to keep the airplane from tipping backward during loading and unloading. Early 727s such as N467US had mechanical locks for the airstair in both the extended and retracted positions to accomplish this function.

However, the crew had evidence that the airstair was not locked, as Mucklow "observed the red indicator light go on the [flight engineer's] panel indicating that the stairs had been lowered." On the 727-100, that light would be de-energized only if the airstair was locked either up or down. (On the -200, a green light was added to indicate a fully extended and locked position.) The ATC transcript indicates the captain's later belief that the airstair wasn't "all the way down", so it's reasonable to assume the warning light remained illuminated.

That the airstair didn't lock down when deployed indicates that it never fully extended. In normal operation the airstair is either downlocked, uplocked, or in transit; there is no way to stop it at some halfway point. It is likely that the air loads simply prevented full extension. A powered 727 obligatorily uses hydraulics to deploy the airstair (unless hydraulic system B is disabled, which there is no evidence of and would have been unacceptably risky given the other systems that depend on it). As long as the operation lever was left in the down position (and we know it wasn't up, or the stair would have retracted), the hydraulics would have continued to try to extend the stair further. However, the airstair hydraulic actuators were not designed with the strength necessary to overcome a 170-knot airstream, especially on early 727s. In fact, some later 727s did away entirely with the mechanical latches in favor of more robustly sealed actuators that could trap hydraulic fluid well enough to prevent movement. N467US did not have this capability, so the extension was limited by the airspeed and subject to fluctuations with changes in the airstream and the weight of Cooper upon the stair.

The inability to fully extend the airstair in flight was even known on the ground beforehand, as the transcript of communications between NW305 and the airline's base at MSP reveal (I cleaned these up):

18:38, MSP: DON'T KNOW OF ANY WAY TO LOCK STAIRS IN AN INTERMEDIATE POSITION.

18:40, NW305: ...STAIRS WILL OPEN ABOUT 20 DEGREES AT 120 KNOTS. IS THAT ENOUGH FOR AN INDIVIDUAL TO ESCAPE THE AIRCRAFT?

18:40, MSP: WITH HIM ON STAIRS WILL OPEN POSSIBLY ENOUGH FOR HIM TO GET OUT. REMAIN UNPRESSURIZED. BE IN LANDING CONFIGURATION WITH FLAPS. SLOW TO [APPROACH] SPEED BEFORE TRYING TO EXTEND STAIRS.

As it turns out, the stair could not be opened much if at all at 170 knots during a climb, and the captain had to "have 'er about down to a hundred and sixty knots" and level off at 7,000 feet to get the resistance low enough. It makes sense that a higher angle of attack would cause a greater air load on the door due to the increased frontal area. It also makes sense that the airflow alone would be insufficient at any speed to completely re-close the door due to the geometry of the empennage and the continued downward hydraulic pressure. Once the door was open, the crew were able to climb again to 10,000 feet and keep the airspeed "in the vicinity of one seventy, one eighty [knots]".

Although the aforementioned hydraulic actuators would have provided damping, the swirling wakes from the landing gear and flaps—not to mention the aircraft turbulence inherent when flying low and slow over mountains in a storm—undoubtedly wrenched the stairs up and down considerably. Cooper's exit has been romanticized as a high-dive into the unknown, but it was more like trying to exit a springboard during an earthquake, with his own weight just exacerbating the problem. We know as much from Richard McCoy, Jr., a copycat hijacker who survived his jump (at the same airspeed) and was later captured and interviewed:

...[McCoy] stood geared up in the open doorway for a very long time before descending the aft stairs. It was almost midnight, the sky was black, and the wind was freezing, yet his hands were sweating. Finally, he was able to collect his wits, take a deep breath and step outside onto the stairs.

As he stepped out, the entire stairway dropped two feet under his weight. Knocked off balance with his 70-pound duffle bag between his legs, he grabbed the right handrail and wrapped both arms around it, desperately holding on. The stairs shook and vibrated. The noise from the jet engines on either side of him was horrendous.

In fact, it was cabin-pressure fluctuations caused by Cooper descending and exiting the airstair that allowed for the determination of exactly when he jumped (8:11pm PST):

Crew reported oscillation of cabin rate-of-climb indicator. This probably due to [Cooper's] weight now on stairs, stairs extended further, resultant effect on cabin pressure.

The FBI's analysis was that "When [Cooper] jumped, the air stairs were forced closed (by outside air pressure) causing an increase in air pressure similar to shutting a car door with the windows up". Although we've established that the door was not forced completely closed and locked, it's clear that even with hydraulic systems operative the airstair was able to hang somewhat freely in the airstream, its deflection affected by air loads, the weight of Cooper, its own weight, and the dampening provided by the actuators.

What was the risk of landing with the airstair deployed?

The crew knew from the cockpit indication that the airstair was neither down and locked nor up and locked. But they had prepared somewhat for the idea of landing with a deployed airstair before they even departed Seattle:

19:27, MSP: IT WOULD PREVENT ANY SUBSEQUENT TAKEOFF IF YOU LAND WITH [THE AIRSTAIR] DOWN.

Mucklow advised Cooper more than once of this fact, given that Cooper had stated intentions to get to Mexico and that Reno was just a necessary refueling stop along the way due to Cooper's wanting to be flown low and slow.

Landing with a deployed airstair could have a range of consequences that had never been investigated or analyzed, so most likely the airline was playing it safe. At the very least, a detailed inspection would need to be carried out before the airplane flew again. If the stair were downlocked, the results of a landing would depend on what failed first. If only the latch failed, you might get away with just dragging the stair, which would cause some exterior damage (and possibly compromise the ability to seal the fuselage up to pressurize) but overall that'd be a relatively minor fix. If the hydraulic actuators failed, you might bleed out one of your hydraulic systems, which is obviously a bigger deal. If nothing on the airstair failed, I suppose you could bend the entire fuselage. I'd also worry about bits and pieces of failed components being rocketed around the empennage or into the cabin.

Fortunately, at this point the crew was safe from the worst outcomes because the stair was not downlocked. Although the hydraulic pressure was still trying to force the stair to deploy further, the airstream at 170 knots prevented that. In fact, as we've seen, the crew knew that even at 120 knots the airstair would not be deployed far enough to strike the ground upon touchdown. That speed is in the ballpark for an empty 727 on landing, but even at a lower speed it's entirely plausible that the airstair did not strike the ground on touchdown, and was only able to fully extend once the aircraft was at taxi speed.

What damage did the aircraft sustain?

Given everything we've covered so far, the damage was probably not extensive. Dragging the stairs along at taxi speed would mean not much more than some sheet-metal repair. Looks like some of the railing paneling sheared away, probably in the air: Airstair damage There's also the placard found in the forest a few years later that got ripped away at some point during the flight.

In any case, the crew was able to easily deplane via the deployed aft stairs:

23:14, NW305: ...WE'LL GO DOWN THE BACK STEPS AND AH AH WE'LL BE TAKING LEAVE OF THE AICRAFT AND SHUTTING IT DOWN AT THIS TIME...

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    $\begingroup$ "The transcript does not prove that the stair was down." Um, it kind of does. $\endgroup$ – Organic Marble Sep 19 at 0:36
  • $\begingroup$ I got out my books and edited my answer below. It is likely the airstair was not in the down locked position. it was most likely in the unlocked state as shown in the picture above. $\endgroup$ – Raffles Sep 19 at 13:04
  • $\begingroup$ AH? Is that some kind of marker or code, because it appears quite often? $\endgroup$ – Peter Sep 19 at 20:33
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    $\begingroup$ @Peter Just a transcription of pilot talk. $\endgroup$ – Peter Schilling Sep 19 at 21:55
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I am a B727 pilot to this day (5,000 hours on type) and I am pretty sure that if one tried to land a 727 with the airstair locked down, there would be a considerable amount of damage and the possibility of a serious accident. The two hydraulically operated struts that operate the airstair are downlocked "over center", They are operated by B system hydraulics which would have been working throughout the flight. Trying to retract the stairs while standing at the rear door with the airstair deployed in flight would be very daunting. You have to hold the handle towards you until the stairs are fully up, at which time the handle moves to an over center position and the stairs remain locked up. If the handle doesn't move to the over center position, the stairs will deploy again to the down position. The only way they won't lock down is if you remove B system hydraulics. In flight it is also possible that the force of the airflow on the airstair at 120 knots could be strong enough to prevent the airstair from reaching the down and locked position. Therefore I suggest that if they did not retract the airstair before landing (which apparently they didn't), and the B system was working normally, the only other possibility is that the force of the airflow on the door kept it floating halfway up.

As a matter of interest, the airstair was removed for the test crash of a 727 in the Mexican desert as this is probably the case.

You can see the over-center downlock in this video. I will make a video of the operation of the handle at the rear door in a few days if there is enough interest.

B727 Airplane General Airstair Operation

B727 Airplane General FE Panel

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The fact is simple geometry would prevent landing a 727 with the aft airstairs in the extended position. These stairs are have almost no clearance from the ground when they are extended. Check the relation ship of the tail strike bumper to the profile of the Aft airstair. You simply couldn't complete an approach at a flat enough angle for a successful landing. So maybe the aft airstair were damaged during the landing? Not possible. The 727 being a T-Tail with 3 rear engines is extremely tail heavy. So much so that the rear airstair doubles as tail support structure for the aircraft when parked or loading. Just the weight of the demountable engines are roughly 4700 lbs each, so we're talking 14,000 lbs independent of the T-Tail structure. When powering back a 727 from the gate the most important rule is to never use the aircraft brakes to slow the rearward roll. The aircraft will sit on its tail everytime. All of this is to illustrate how strong the aft airstair structure is on the 727 as well as how critical weight and balance limitations are on this particular aircraft. The conclusion drawn from this information is reports of landing a 727 with the airstair extended cannot be true.

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  • $\begingroup$ A bit of formatting would go a long way toward making this more readable. Maybe that's why I'm not seeing how your reasoning supports your conclusion that one cannot(?) land a 727 with the rear stairs open. Also, just because one shouldn't doesn't mean that they didn't in this one very special case, and you don't seem to address the case of the specific, hijacked aircraft that was asked about. $\endgroup$ – FreeMan Sep 15 at 17:33
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    $\begingroup$ Also, please note Peter Schilling's answer (posted after yours) that includes ATC transcripts indicating that they in fact did land with the rear air stairs open. The stairs did hit the tarmac, but, it seems only once the aircraft slowed to taxi speed. It seems that your conclusion is flat wrong. $\endgroup$ – FreeMan Sep 18 at 18:22
  • $\begingroup$ Basically his answer is correct. unless they landed flaps up with a very flat attitude or disabled the B System hydraulics so that the the stairs were floating. $\endgroup$ – Raffles Sep 18 at 23:30
  • $\begingroup$ @Raffles as you admit in your answer, it's possible that the stairs didn't lock down. This is corroborated by the ATC transcript provided in Peter Schilling's answer. While I agree with both of you that landing with the air stairs locked down would cause significant damage, the facts of this incident show that they never did lock down, therefore the final conclusion in this answer that it "cannot be true" is categorically wrong since history proves that it is actually true. Also, causing damage and not being possible are 2 different things. $\endgroup$ – FreeMan Sep 21 at 15:13
  • $\begingroup$ @FreeMan you are right about the last sentence. The author should revise it. $\endgroup$ – Raffles Sep 21 at 15:23

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