Boeing 707-320C
It is a few years since I last read this document, but you may be able to find the answer here: Gary Sommerville’s DC-8 experience. updated OCT 2018.pdf - Google Drive
"The best airliner in the world would be designed by Lockheed, manufactured by Boeing, sales & marketing by Douglas" says quite a bit ...
Not sure how they got the compressing power away from the engines
Each of those chin scoops have three holes. There is a large opening in the middle which takes in air for the air-to-air heat exchanger on that side. There are also two smaller holes that are the individual inlets for the turbocompressors. On the DC-8, there are a total of 4 turbocompressors. The Boeing 720 series had two turbocompressors and most 707 series aircraft had three.
It should be pointed out that the DC8/Boeing 707/720 generation of aircraft didn't bleed air directly from the engines for pressurization and air conditioning. Rather, a small amount of engine bleed air was used to spin turbo-compressors which drew in fresh air, compressed it and raised it's temperature. This air, cooled via heat exchangers and freon units, was directed to the cabin distribution system.
The Boeing 727, 737, and DC-9 generation of planes using JT8 series engines were the first to use bleed air from the engine itself, through air conditioning "packs" to directly pressurise the cabin and for temperature control.
In later years, when the JT3 engines, on DC8s, were replaced with CFM-56 powerplants, the turbocompressors and freon cooling units were removed and replaced with "packs" that allowed engine bleed air to be used for temperature control and cabin pressurization. The DC8 chin scoops were modified to close off the turbocompressor inlets.
It should be pointed out that the DC8/Boeing 707/720 generation of aircraft didn't bleed air directly from the engines for pressurization and air conditioning. Rather, a small amount of engine bleed air was used to spin turbo-compressors which drew in fresh air, compressed it and raised it's temperature. This air, cooled via heat exchangers and freon units, was directed to the cabin distribution system.
The Boeing 727, 737, and DC-9 generation of planes using JT8 series engines were the first to use bleed air from the engine itself, through air conditioning "packs" to directly pressurise the cabin and for temperature control.
In later years, when the JT3 engines, on DC8s, were replaced with CFM-56 powerplants, the turbocompressors and freon cooling units were removed and replaced with "packs" that allowed engine bleed air to be used for temperature control and cabin pressurization. The DC8 chin scoops were modified to close off the turbocompressor inlets.
It is a few years since I last read this document, but you may be able to find the answer here: Gary Sommerville’s DC-8 experience. updated OCT 2018.pdf - Google Drive
In the mid-80s, my family and I returned to Canada after six years overseas in Brisbane and Jakarta. My kids were experienced world travellers by then, having flown round the world three times.
My son who was six, was in his first year in the strange-to-him environment of a Canadian Elementary School. His home-room teacher told us that one day she showed the class some CP Air travel posters of various destinations across Canada. She described how my son was completely disinterested in the proceedings, until she showed the class a poster of Hong Kong, at which point he became very animated and told the class in great detail about Hong Kong and in particular mentioning the smell as the aircraft landed at Kai Tak!
If I'm not mistaken it was not reverse "thrust" as the DC8 would only operate idle reverse, just on two of the four engines. Of course, one would not know from the cabin seeing the reversers deploy that this was the case. I read the DC8 was the first jet to do this. I don't know how much retarding force idle reverse actually provided.
Never flew the DC-8 but I believe it did not have speedbrakes/flight spoilers - hence inboard engine inflight reverse. The company I flew for had 2.
On a "dead-heading" sector cockpit ride back home into Stansted, London ATC's descent clearance "Cross Detling FL120 or below" saw it applied and I recall impressively down the old bird went...
Being essentially drag based, I imagine it's effectiveness was airspeed related, drag increasing at the square of the speed etc. I think Douglas (or McDonnel-Douglas by then) banned it's use in flight eventually over concerns about turbulence over the tail.
Meanwhile, back to the 707: Those turbo-compressors were presumably the source of air for the conditioning system. Powered by bleed air when the engines were running, could they provide cooling air on the ground with the engines shut down? Pneumatic manifold perhaps?
The 707 was an incredible piece of work. I recall reading an article years ago suggesting it should be considered one of the 10 best engineering solutions ever achieved. It took all sorts of incredible inventions, the jet engine, the swept-wing and so on, wrapped them up and continued to improve them, in a thoroughly workable, practical globe-spanning package. A huge tribute to Boeing, its engineers, its people and the airlines that originally flew them.
Using airborne reverse of the inboard engines on the DC8 was very efficient, but could feel uncomfortable. I think I only used it a couple of time in four years on the type.
The CFM powered DC-8-70s were prohibited from using reverse in flight. I was on the jump seat of a UPS DC-8 descending into STN and the captain pulled the inboard reversers up, the FE slapped them down again.
The 707 was an incredible piece of work. I recall reading an article years ago suggesting it should be considered one of the 10 best engineering solutions ever achieved. It took all sorts of incredible inventions, the jet engine, the swept-wing and so on, wrapped them up and continued to improve them, in a thoroughly workable, practical globe-spanning package. A huge tribute to Boeing, its engineers, its people and the airlines that originally flew them.
I did read that there was a Boeing board decision in the early 1950s to buy their own wind tunnel. For US tax reasons it was attributed as an educational tool, in the ownership of the Washington State University in Seattle, but Boeing paid for it and ran it. With its own building, would have been a considerable expense. Douglas meanwhile didn't buy one, but just bought time on the NASA etc wind tunnels, and I read that accounted for some differences. The DC8 did have a range of aerodynamic shortfalls at the margins, and various modifications over time. Northwest, for example, chose the DC8 early on, and found it couldn't as promised do their key transpacific route from Seattle to Tokyo, with no alternative to going well out of the way and fuel stopping at Anchorage, Alaska, which didn't fit with the timetabled connections at both ends. Very early on Northwest dumped their DC8s and bought the start of a substantial 707 fleet.
Washington State University is on the other side of the state in Pullman - UW and WSU are big rivals so confusing the two can be fighting words in some quarters
Just a minor clarification - it's not "Washington State University in Seattle" - it's the University of Washington in Seattle.
Washington State University is on the other side of the state in Pullman - UW and WSU are big rivals so confusing the two can be fighting words in some quarters
Washington State University is on the other side of the state in Pullman - UW and WSU are big rivals so confusing the two can be fighting words in some quarters
I always enjoyed seeing the 707 and 720 on charter and inclusive tour duty in the 70s and 80s. Laker, Monarch, JAT, Dan Air, British Airtours, Air Atlantis et al. And Aer Lingus too. Not necessarily operating on routes for which the aeroplane was designed but, in many instances, bought and well and truly paid for. Lovely aeroplane. And the 727 too.
Tax, Boeing and wind-tunnels:
As I understand it, the profit Boeing made from selling B-17s to the US government in WW2 was colossal as too was the tax due on those profits.
By investing in items like the wind-tunnels talked of here, R&D etc, it was able to write-off the costs against its tax bill.
That investment brought about the B47, the 367-80, the 707 and ultimately a few more magnificent aeroplanes.
Please could we have the old Boeing co. back but preferably without another WW to generate the profits to offset against tax to bolster R&D?
As I understand it, the profit Boeing made from selling B-17s to the US government in WW2 was colossal as too was the tax due on those profits.
By investing in items like the wind-tunnels talked of here, R&D etc, it was able to write-off the costs against its tax bill.
That investment brought about the B47, the 367-80, the 707 and ultimately a few more magnificent aeroplanes.
Please could we have the old Boeing co. back but preferably without another WW to generate the profits to offset against tax to bolster R&D?
Boeing also benefited from the organised trawl of German research data in 1945 - it was a major influence on the wing design for the B-47
Had one pax. flt. in an Air Canada DC8 , into Toronto . Noticed the reverse thrust come in ...'' Hello , it's just like our Tridents '' we said .
Trident engines 1 and 3 could be put into reverse and 10,000 HP RPM applied . Extremely effective , 365 kts IAS , Speedbrake and 10,000 reverse gave descent rates of over 17,000 ft per minute .
Apols for 707 drift .
rgds condor .
Trident engines 1 and 3 could be put into reverse and 10,000 HP RPM applied . Extremely effective , 365 kts IAS , Speedbrake and 10,000 reverse gave descent rates of over 17,000 ft per minute .
Apols for 707 drift .
rgds condor .
Talk of 707 wing design also brings to mind a point made in that DC8 article linked above, where the writer states that as the DC8 didn't have quite the wing sweep of the 707, it didn't suffer to the same extent from the various aerodynamic issues that seemed to arise from this. And although not an aerodynamicist myself, it does seem that current generation models do not have the same amount of sweep that the 707 did. Could it be that Boeing put in a bit too much compared to the optimal ?
For example, the A321XLR, which seems to do pretty much what a 707 did in terms of size and range, has sweep of 25 degrees, compared to the 707 35 degrees.
But that's pretty much (given that I do know a bit more about finance than aerodynamics) what governments all round look to encourage, and do, that instead of 'too much' profit, paid back to shareholders who often don't know how to spend it wisely, it instead gets spent on developing a successful business further, buying new capital equipment and thus stimulating the rest of the economy, and such like, for both the originating business and their suppliers of new capital equipment. As here.
It has been a point of discussion in recent times that whereas major businesses in the USA and principal European countries were offered this because they tended to spend on such items within their own country and economy, to the advantage of those who their government represents, nowadays such purchases are far more commonly imports from overseas, not giving the same advantage.
For example, the A321XLR, which seems to do pretty much what a 707 did in terms of size and range, has sweep of 25 degrees, compared to the 707 35 degrees.
Tax, Boeing and wind-tunnels:
As I understand it, the profit Boeing made from selling B-17s to the US government in WW2 was colossal as too was the tax due on those profits.
By investing in items like the wind-tunnels talked of here, R&D etc, it was able to write-off the costs against its tax bill.
That investment brought about the B47, the 367-80, the 707 and ultimately a few more magnificent aeroplanes.
Please could we have the old Boeing co. back but preferably without another WW to generate the profits to offset against tax to bolster R&D?
As I understand it, the profit Boeing made from selling B-17s to the US government in WW2 was colossal as too was the tax due on those profits.
By investing in items like the wind-tunnels talked of here, R&D etc, it was able to write-off the costs against its tax bill.
That investment brought about the B47, the 367-80, the 707 and ultimately a few more magnificent aeroplanes.
Please could we have the old Boeing co. back but preferably without another WW to generate the profits to offset against tax to bolster R&D?
It has been a point of discussion in recent times that whereas major businesses in the USA and principal European countries were offered this because they tended to spend on such items within their own country and economy, to the advantage of those who their government represents, nowadays such purchases are far more commonly imports from overseas, not giving the same advantage.
Last edited by WHBM; 27th Mar 2023 at 17:30.
It still almost ended up in tears when they lost tail effectiveness and had to use stab trim to pull out of the dive.
BTW, I spent a lot of time looking through 747-8 flutter flight testing data. I didn't see anything at Mach 1 or above, but there was a whole lot of data in the 0.99 Mach range.
Here's a link to the Mach 1 story:
https://www.smithsonianmag.com/air-s...onic-27846699/
I Was There: When the DC-8 Went Supersonic
Notably a DC8-40, with Rolls-Royce Conways (like the 707-420). Wonder why they chose that minority variant. Does this make Rolls the only engine manufacturer whose commercial production products have gone supersonic?